If you are standing, the boys go straight north between the pelvis and the musculature in front of the pelvis. For many there is a bit of a depression in the pelvis there so when you tuck the skin is pulled a bit tight and held there. That's why a tight pair of panties and jeans well hold everything in place. For those without that bit of depression in the front of the pelvis and/or for those with bigger boys, they will make a bit of a bump until they get used to being pressed a bit by the panties and/or jeans.
tina