2 Part Technique - Passing the half guard becomes considerably more likely when you can establish Underhook and Head Control and stabilize his upper body. If the opponent begins to dig for his own underhook against yours, quickly repummel and counter his threat. If he begins to win this battle by reaching deep enough for the repummel to fail, quickly squash his arm below his elbow so he cannot dig any deeper. Use your other arm to lock out space between your bodies for you to use the repummel without the risk of losing the position or getting your back taken. If he manages to nearly secure a full-on underhook from half guard -deep enough for the first two defenses to fail, quickly create a frame by apply a crossface against his chest and neck so you can ward off further danger and reclaim your underhook by pummeling.