If you are drawing up blueprints for a machine the two are essentially identical. You choose whichever makes sense for the joint you need, but they are essentially identical on the blueprint.
If you are making the card reader for automated machines, knitting, weaving, and playing a piano are virtually identical - you just move some lever in response to a hole. Someone working on a different part of the machine cares about the difference, but to the card reader they are identical.
This reminds me of the Citycorp Center near-disaster:
> LeMessurier's original design for the chevron load braces used welded joints. To save money, Bethlehem Steel proposed changing the construction plans to use bolted joints, a design modification accepted by LeMessurier's office but unknown to the engineer himself until later.
> With the tuned mass damper active, LeMessurier estimated that a wind capable of toppling the building had a one in fifty-five chance of happening any year. But if the tuned mass damper could not function due to a power outage, a wind strong enough to cause the building's collapse had one in sixteen chance of happening any year.
