I’m frequently amazed at what happens when I hand a sharp full-size handsaw to a fellow woodworker for a test drive. Nine times out of 10 they clamp something in the bench vise and then struggle mightily to get the saw to cut smoothly. No wonder. Using a handsaw without a sawbench is like trying to use a router without securing your work. You can do it in a pinch, but your results usually suffer.
Sawbenches are kneecap-level platforms that fully exploit both the length of the saw and your body to make sawing efficient and fast. The height (mine is 19-1/2″ high) allows you to use the full length of the teeth without hitting the floor on the downstroke or from the saw disengaging from the kerf on the return stroke. The height also allows you to use your two legs as the most ingenious clamp and stop ever invented.
One knee holds the work down and the other knee immobilizes it laterally.