A sexual act that is performed by placing the penis inside of the vagina and not performing any further action. It is customary to set up a buffet table next to the bed so that neither party becomes hungry during the often hours-long ordeal. One is not allowed to call or text while sheathing, as sheathing is the ultimate sign of commitment towards a sexual partner. It is perfectly fine to sleep while sheathing. The sheathing ends when: the penis becomes pruned; either party has to urinate, because the result of urination while sheathing would be like putting a thumb over a hose; death of either party; the end of the relationship between the parties. It is not permissible to orgasm while sheathing.
Mark's heart was filled with joy when his girlfriend asked if he would consider sheathing with her.