Various knob types that work with any bolt that has a 1/4-20 thread.  These work great for mounting anything that you want to install or uninstall quickly.  Commonly used with T bolts for installing seats and accessories on Fishing kayaks.

The Mighty Knob has plastic 1/4-20 threads that tighten but do not lock.
The Tri Knob Locknut has a 1/4-20 stainless steel locknut nested inside.
The SpinGrip knobs feature ribs for spinning, finger holds for gripping, and a 1/4-20 stainless steel insert that tightens but does not lock.
The Two Arm has a 1/4-20 brass insert that tightens but does not lock.