Some of the gaffs I sell can only be used if you "tuck". This is the process by which you push your testicles up into the small recess at front of your groin at the top of your scrotum. I have attached the following guidelines from the manufacturer - for your information.
Guidance from manufacturer:
The way to wear our underwear is very easy, just follow these very simple steps:
- Insert the testis in the lower part of the abdomen; with the help of your fingers, raise them above, toward the pubis.
- Stretch the scrotum's skin between your legs, as straight as possible. For the penis, follow the same stage.
- Put the underwear; and adjust it untill you feel comfortable and the "mons Venus "looks flat.
With those little tricks and our lingerie, you will feel comfortable all time.

Please Note; As a genetic female it is impossible for me to advise on the pros & cons of tucking. Although it is a fairly common practice I cannot really provide any assistance on this matter.