The Complete Vac-U-Lock Users Guide
Last Updated on December 1, 2025
The Vac-U-Lock by Doc Johnson is a unique brand of strap-on dildo that has plenty to offer couples looking to spice up their sex life in quality & style.
There are many different harness kits on the market, but very few have the vast range of options and high quality luxury that this harness system offers.
Table of Contents
Today's guide will cover step by step instructions on how to mount and remove the accessories, how to use the strap on harness and how to care for your items with talc powder. I'll discuss new upgrades with Doc Johnson suction cup dildos & offer tips and advice to make your experience more enjoyable.
What Is Vac U Lock?
Vac U Lock is Doc Johnson's exclusive brand of “plug and adapter” style strap on harnesses with a vast selection of compatible dildos & accessories.
The line of Vac U Lock products feature a series of attachments with a female adapter that fits onto the male adapter connected to the front of the strap on. The system is comprised of several different items that are compatible and interchangeable. Couples can mix and match accessories to customize their own sexual desires.
Vac-U-Lock Accessories Include:
- Unisex & adjustable strap on harness
- Ultra realistic UR3 dildos
- Vibrating & non-vibrating attachments
- Firm rubber attachments
- Dildos that look like a penis
- Soft jelly & silicone dildos
- Adapter that connects to the harness with metal snaps
- Inflatable ball with adapter
- Talcum powder
- Vast range of attachment sizes & dimensions
How to Mount the Dildo
Mount a Vac U Lock dildo to the harness plug by twisting it on to the adapter plug with your hand while supporting the harness with your other hand.
Sprinkling talcum powder inside the hole on the base of the dildo prior to mounting will make it easier to attach the dildo to the plug. Further details on this can be found below, so keep on reading!
Originally it may appear obvious how to mount the toy onto the compatible harness adapter, but you'll soon realize that it has a super tight fit! This is no mistake, it is designed this way to be sure the attachment does not rotate on the plug during sexual intercourse.
It will stay in place no matter how rough your sex play or how often you walk around while wearing the strap-on. Watch the accompanying video demonstration, I show the following steps in order to correctly mount the attachment.
In the demonstration use a rubber penis which twists on with a firm hand, but I'm by no means have pumped biceps and it's easy for my thin arms to twist in place. You may need to use extra force if you have a firmer accessory, but as stated previously, the powder makes it slide better.
Step by Step Instructions:
- If the red adapter is not connected to the harness already, press it on with the 4 metal snaps.
- Holding the dildo upside down, sprinkle 1 tsp of talcum powder inside the hole on the bottom of the attachment.
- Holding the dildo sideways, insert your finger into the hole and twist it around to spread the powder evenly inside the hole.
- Do not return the dildo to an upright position or the talc will fall out of the hole!
- With the dildo sideways, twist it back and forth onto the adapter plug slowly while maintaining even pressure as you push it on.
How to Remove the Dildo
To remove the dildo from the plug, pull it off in a twisting motion with one hand while supporting the square base with your other hand.
Important tip: Do not pull it straight off, this will stress the rubber or silicone material of your toy. You must “twist” it to remove.
Before I explain the steps on how to remove the attachment from the strap on, I'm assuming you've already put it on using my steps listed above. The secret is to make sure you have used talcum powder inside the hole.
If you didn't use powder, the pressure inside the 2 pieces creates a strong vacuum and it can be difficult to remove! If you did not use powder, the steps are still the same, but may be trickier to pull it off.
In my experience, the rubber toys create stronger vacuum connection than the silicone toys. It's possible to remove a silicone toy without using powder, but it's still recommended to use it because you don't want to over stress the surface of the toy by pulling on it all the time, it can eventually tear.
Step by Step Instructions:
- Grab the dildo at the base, and slowly twist it as you pull away from the harness.
- Do not squeeze the dildo too hard at the base or it may be difficult to remove.
- Using consistent twisting motion is more effective that pulling it straight off, plus its gentler on the material, especially if you are using a UR3 silicone as the material is more delicate than rubber.
Can Men Wear the Harness?
Yes, there is a large opening at the bottom of the harness leaving more than enough space for a man's penis and balls to hang freely below. As such, this is one of the most suitable option for guys.
Thanks to this innovative crotchless design, men can easily wear it without discomfort. It is one of the most popular strap on harness kits of all time because of its unisex design - it literally fits anyone! It is also the most luxurious and best strap on penis a man can wear, both in terms of comfort for him and realism for her.
In the photo above, you'll see the wide open crotchless base. There is an extra long and wide opening at the bottom of the panty style harness with plenty of space for a man's penis and testicles to hang below unimpeded, untouched and clear out of the way from the action happening above and the harness material to the side.
As such, this is a popular option for men with erectile dysfunction because his flaccid penis and scrotum hang freely below. If the man can get an erection, then there's plenty of space down there too. The dildo will fit higher on the pelvic bone so an erection can make it's happy appearance below the dildo.
How to Put it On
Attach the dildo before putting on the harness. Once the harness is on your body, adjust the belt at your hips and tighten the buckles to accommodate your waist size.
Step by Step Instructions:
- Attach the plug and dildo by following the instructions above.
- Feed the waist straps through the connectors.
- Put it on by stepping into it like you're putting on underwear.
- Pull the straps at the hips to adjust to your waist size.
- Position the dildo so that the flat back of the plug rests just above your pubic bone. Note: It should fit higher than a normal strap on because of the weight of the dildo & plug.
- Re-adjust the straps to tighten the harness firmly on your body according to this new dildo position.
- Tuck the rest of the straps inside the back, or you can trim them with scissors to fit your waist size specifically.
How to Use It
Lubricate the dildo shaft thoroughly with water based lubricant before having sex. Regardless of the material you've chosen either soft or hard, rubber, jelly or silicone, you'll still need lots of lubricant. Is simply makes the whole experience better and more comfortable for the receiver.
One of the things you may notice is that the combination of plug & dildo feels quite heavy, so as noted above, you'll want to fit the dildo higher than you would on most other strap-ons. It should sit over the pubic bone.
An essential tip to mention is to never use silicone lube with the UR3 dildos because it can melt with the silicone compounds of the toy. It's always wise to choose water base lube, furthermore, it won't stain your bed sheets or the harness material whereas silicone lube can create “oil” stains in fabric.
What are Vac U Lock Adapters?
The Vac U Lock adapter is the red plastic piece that attaches to the harness and holds the compatible toys in place.
Most strap on dildos simply have a rubber or metal O ring that snaps onto the harness, or sometimes they are sewn into the fabric. The advantage here is the toy stays in place without moving around. This system can withstand active sexual motion compared to more budget options available for sale.
If you purchase any toy now, it will fit with any current adapter plug, but if yours is really old (10+ years old), it may not be compatible anymore. Vac U Lock sex toys and plugs are all compatible now as the brand has moved to improve consistency to make it easier for users.
What is Vac U Lock Powder?
Vac U Lock powder is Doc Johnson's own brand of talcum powder. It acts as a lubricant to assist in removal of the attachments from the harness plug. It's unscented and will not leave greasy reside.
Why use powder? As noted in the step by step instructions above that explain how to use the dildo, when the male and female adapters are connected, it creates powerful vacuum inside, so the talcum powder acts as a lubricant to make it easier to remove the dildo from the strap on.
You do not have to use Doc Johnson's own Vac U Lock powder; any type will do, but this one is a popular choice for couples because it does not small like baby powder. In our opinion, using talcum is an essentially important step that will prevent your accessories and the harness material itself from overstretching and tearing during repeated application and removal.
Selecting a Compatible Doc Johnson Dildo
Adult sex toy connoisseurs may have noticed that many Doc Johnson dildo suction cups have changed. They are no longer a continuation of the same material, now they are an entirely separate suction cup that can be removed from the dildo. Thanks to this innovation, almost all of their dildos are compatible with the Vac-U-Lock plug.
We think this is an absolute ingenious invention and give great kudos to Doc Johnson for this improvement because they've opened up a whole new realm of ultra realistic suction cup dildos of all sizes, colors and shapes that can be used with their strap on harness. No longer are we limited by a small handful of attachments to choose from, now virtually any Doc Johnson dildo can be connected to their plug.
At the time of this writing, they are still in the process of liquidating old stock so make sure to double check to verify if the suction cup is removable before choosing one.
Who Uses Vac U Lock?
The most common users of Vac U Lock is older couples. Men will wear the strap on and use the dildo on their partner, the UR3 mateiral is one of the most realistic-feeling options for couples who want a lifelike experience.
Furthermore, Vac U Lock strap on is the most comfortable for men to wear. The large opening at the base leaves more than enough room for his flaccid penis & testicles to hang below. The position of the attachment dos not impede with his scrotum below and he won't experience any chafing or pinching. Super cozy for him!
Another benefit of this system is the vast range of compatible attachments enabling each couple to customize their own kit according to their preferences. To find the right compatible attachment, check out our guide listing the best Vac U Lock strap on dildos complete with a side by side comparison of the most popular styles in our catalog.
