My Knife Jig (short and long) do not have locking knob to prevent them from turning as seen on the demonstration. Is there some retrofit for these older jigs to be able to lock them from moving in and out?
While you can buy replacement heads for your knife jigs, You might find it to be less expensive to drill and tap the heads that you already have. The plastic machines very easily. 1/4" x 20 tpi knobs are available at almost any hardware store.