We recommend keeping an extra wingnuts handy in case one gets lost.
TIP to keep your knobs on! Add some teflon plumbers tape to the threaded post, as shown in last photo. You can get this at any hardware store. It increases the friction and helps keep the knobs tight. Just add a little of the tape to the screw part and then put the knob on the harness. Works like magic to keep it from loosening.