BOM:

• 1x optical endstop
• some garbage (spring, m3 screws, 3mm pin)

Assembly:

• You'll need to cut the endstop flag about 3mm to allow full range of movement. Use file to fine tune endstop activation point.
• Everything else is trivial

Operation:

• Slam your x carriage along the x axis against some kind of kicker to deploy probe.
• Do your probing stuff
• Push down along z axis against something attached to heated bed to retract and lock pin all the way up

Exampe:

https://youtu.be/4gcxNkhXoDg

Source: https://cad.onshape.com/documents/fe7ef93aeb21687c26dace27/w/ac0cc948d4102d237be16f5c/e/1572b5aa1850fcffd6aad131