By never opening both members at once. As the front stop retracts to release the leading part, the rear stop is already extended into the track behind it, so the queue is held while one part leaves. That overlap is built into the mechanism, which is why a two-cylinder arrangement improvised from separate stops usually leaks a second part on the first fast cycle.

Blade or knife types that slide across the track, pin types that drop into the gap between parts, and rotary pocket types that carry one part round in a recess. Blades suit flat and headed parts, pins suit parts with a clear gap between them, and rotary pockets suit small parts at high rates because there is no reciprocating mass.

It loads the blocking member and it changes how the leading part behaves on release. A long full track pushes hard enough to bind a blade in its slot; an almost empty one may not present the next part at all. Tracks are usually designed with a back-stop or a level sensor so the queue stays within a working band rather than running from full to empty.

The mass being reciprocated and the settling time of the part after release. A blade escapement has to accelerate, stop, reverse and stop again within the cycle, and the part then has to reach a known position before the next operation. Rotary types avoid the reversal and generally reach higher rates for the same part.

Through a designed access point: a hinged track cover, a retractable side rail or a manual override on the escapement valve. Because a jam usually happens with a part wedged against a blocking member, forcing the mechanism is what breaks it. Machines that expect jams have the escapement mounted so it can be withdrawn from the track rather than dismantled in place.

Yes, if the blocking member strikes a finished surface or if the part is released onto a hard stop. Soft-tipped blades, cushioned end positions and a controlled drop into the nest are the usual answers. Delicate parts are often better handled by a rotary pocket, which supports the part through the transfer rather than stopping it dead.

It needs to know a part has actually arrived, which is not the same thing. Sensing the escapement's own stroke confirms the mechanism moved; a sensor on the nest confirms a part is there. Cells that interlock only on the escapement stroke will continue cycling through an empty track without noticing.