When you find yourself in the half mount or top half guard position, securing an underhook is very important.
In jiu-jitsu things seldom go as planned, and an experienced half guard player can beat you to the underhook and threaten you with all types of escapes and counters. The primary threat is having your back taken.
Here are two half guard passes you can use when your opponent gets the all-important underhook. Both of these passes work well with or without the gi.
Reverse Sit Half Guard Pass
Back Step / “Capoeira” Half Guard Pass