Innocent question re Half-cock position on wheelguns

[Carl N. Brown]

Most rebound safeties require that the trigger be held back
before the hammer can go forward to strike the firing pin:
so if the hammer catches on clothing and slips, it would
only fire if you had your finger pulling the trigger at the
same time. There is a mechanical block actuated by the
trigger on Colts, Smiths and Rugers. The designs are different
but the end result is the same: you must have the trigger
all the way to the rear before the hammer can strike the
firing pin.

Some older or cheaper designs are not as safe, but modern
revolvers are designed to require a deliberate trigger pull
before they can fire.