I am guessing that is to hold the plane before launching. We have to use a holding device too. I use the table, and a lot of my stuff is hand launched. Sometimes I bring a string like most of the guys. It is pretty clumsy that way. Fortunately, I only have one bigger plane that needs the lasso. The monster plane guys sometimes use a couple stakes that they step on to push into the grass. At my old field there was a guy made a U shape fork that had a foot pedal to disengage the plane. It was pretty fancy aluminum that was CNC machined I think.