Schacht warping pegs come in several styles:
The Regular clamps to a table or counter; the single shaped peg placed at one end of the warp length and the pair of pegs placed at the other end, spread as far apart as the warp is long. Comes with 2 clamps.
The Single Peg with Clamp clamps to the table opposite your Rigid Heddle Loom and is used for the direct warping method, where you do the warping in one step (instead of winding and measuring it, and then putting it on the loom). This method is demonstrated in the video below, with a Schacht Cricket Loom.