Anything that only requires a single gesture to operate - e.g. a push button covered by a flap (like on the missile launch systems in films) which requires two actions (1. lift flap, 2. press button) would be out.

   - Andy.

So, what is a single gesture?

Z.

So, what is a single gesture?

Z.

e.g. push, pull, twist, or is it? Normally you would push (hit, kick) an emergency stop button. Arguably, if you have to grip it first, and then pull or twist, it is 2 actions. Rotating a lever could be achieved in one action because it would not necessarily have to be gripped first.

I think that a lever has first to be gripped then pressure applied to rotate it. So that is more than one simple action. The same applies to a rotary switch.

Z.

If you think of a (modern) door handle (as opposed to an old-fashioned knob), it can be operated by pressing one's knee or foot on it if, for example, you are carrying something with both hands. Of course, that doesn't help if you are on the same side as the hinges; and it is not the intended means of operation in any case. If it was intended to be foot-operated, it would be a door pedal rather than a handle.