The screw-up is basically a recovery technique that evolved from over-vertical stern squirts. It is probably one of the most useful techniques for boaters because it can be used virtually anytime your bow passes vertical. Essentially it is a way of avoiding a full blown capsize when your boat passes vertical. When your playing in a hole pulling off a screw up may prevent you from being flushed out or even munched by the wave.
As with all moves they need to be practiced. The best way to practice this move is to put your boat into a position where it is going to pass vertical. The best a safest way to do this is on a nice deep eddy line and throw a stern squirt. The idea is that the move will be ingrained and can then be used on the flat or even in a hole whilst cartwheeling.
So here we go, you’ve found a suitable spot to practice. From the eddy cross through the eddyline and pull an aggressive stern squirt with a powerful back sweep. As soon as you feel the boat going past vertical start to roll in the direction you are turning. So if you started the squirt with your sweep on the left you’ll need to roll on your left. This is a lot easier than fighting against the direction the boat is already travelling in!