Underwear to be converted (I am using boxer briefs in this tutorial, but this should work on any "men's" underwear!)
Sacrificial underwear (these do not need to be "men's")
Either a needle or a sewing machine
Pins or basting glue/some kind of temporary fabric glue
My sewing skills are pretty beginner-level, but if you've never sewn before, this is a modified version of the idea from this video, which explains hand-sewing as well! imo this is simple enough (and similar enough) that you can probably attempt this tutorial after you watch that one.
What we're going for is a pouch in the front of the underwear, using the shape of the crotch they already have. This is a pair I made with fabric that matches it exactly (turned inside-out so you can see the pocket):
For this tutorial, I chose a sacrificial pair that contrasts a little bit, just so yall can see what I'm doing.
I'm converting the underwear on the left into packing underwear. I've chosen a sacrificial pair that I think I can match nicely to them, plus some thread that matches them both. You truly do not need to be this picky about it.
First, I'm going to deconstruct my sacrificial pair:
Cut along the yellow lines to separate out the crotch, elastic waistband, and the butt. (I cut on the outside of the seams here, so the seams were removed with the crotch.)
We're gonna get rid of the crotch, because it's cup-shaped & won't lie flat. The butt fabric will be perfect for that!
But first: the waistband.
This is the part that makes this design work so well! Let's remove some excess fabric from the waistband that my scissors couldn't get with the seam ripper (this is optional)
You want about 6'' of the waistband to form a strap, which will hold your packer in place inside the pouch.
My packer is a Mr. Limpy, which works well with these harnesses. This should also work with some packers that don't have balls- esp sock packers- but if you use the soft cup-shaped packers, I might be concerned about the strap compressing them. Whether you fiddle with the design, or just leave the strap out altogether, is up to you!
I played around with mine and found that it worked best to place the strap about 3'' up from the bottom of the crotch, but this may be different on your body & with your packer. Once you figure out placement, you're going to:
Turn your underwear inside-out
Measure & place your elastic strap (I like to go 3'' above the bottom seam of the crotch) (It's important that your elastic is longer than your crotch is wide!)
(Make sure you do not pin your crotch to your ass.)
Now, you're going to place the butt fabric from your sacrificial underwear so that it covers the entire crotch, leaving maybe a quarter inch or so of room from the waistband. I also recommend placing one of the hemmed edges from the leg holes at the top here, so you don't need to hem it yourself.
(Blue lines are the crotch seams underneath, and the purple is the elastic, with yellow pins. I feel x-ray helps me understand what's going on.)
And pin! (With more x-ray so you can see where everything should be)
Turn the whole deal right-side-out again, and sew along the existing crotch seams:
This will hide your sewing, which I think is a nice touch.
When you're done, turn it inside-out again and cut off the excess fabric (you can cut pretty close to the seam here)
I decided to do an overcast stitch around the inside hem, just to help prevent fraying and make things look more finished. If you're hand stitching, you probably do not want to do all that, but you can use a zig-zag stitch for a similar effect if you're particularly masochistic/determined.
I find the strap really helps keep things in place no matter what I'm doing, whereas the pair I made without one needed a lot more readjusting. I'm also a huge fan of how subtle the changes are! Even when I go to the bathroom, I'm not reminded of how Different And Strange my underwear are. Feels good.
If you come up with any tips or changes, or if you decide to make these and want to share/provide feedback, please add to this post & I will try to share!