This pin is made for dropsetting during your workouts.
How to use:
Step 1: Slide pusher back

Step 2: Lock with arm

Step 3: Insert metal pin into desired weight

Step 4: Insert arm into the hole below

Step 5: Start your set

Step 6: Let go of the tension on the cable as the pin will fling itself out of the weight

Part list: This pin requires the following parts:
1x Arm

1x End cap

1x Housing

1x Pusher

2x Pegs

1x 130mm long 8mm thing iron rod

1x Spring

Assembly:
To assemble the dropsetting pin:

Step 1: Test to see if the pusher fits freely into the housing

Step 2: Align the square holes on the pusher with the guiderails of the house

Step 3: Glue pegs to the pusher

Step 4: Aquire and insert spring (I made my springs by heating up some 2.85mm filament and wrapped it around a metal bar)

Step 5: Insert metal pin into front hole (I threaded my pin and hole, but you could probably also just heat up the metal pin and melt it in place)

Step 6: Mount arm on the two pertruding pegs on the house