We do not always cut the entire board lengthwise on a stationary circular saw. Sometimes we just cut the board to a strictly defined length, leading it along the guide, e.g.. from a square timber attached to the table. In this case, a convenient stop can be an ordinary carpentry clamp clamped on the guide in the intended place. The sliding board will lean against the squeeze at some point, and this will determine the length of the incision. The clamp can be replaced with a nail driven into the side edge of the guide.
