When you have suspect(s) sit on a curb, have them extend their legs and cross their ankles. Before they can get up, the suspect needs to uncross his/her legs and bend at the knees. Either of these actions are easily identified and should be immediately corrected with a “keep your ankles crossed” command. This not only is a low-key way to keep people under your control, but also verifies to the suspect that you are paying attention to his actions.