A Fall

A_Fall is a code pointer used in the explode and death animations for the Player and various monsters.

removes the SOLID flag from the object it is attached to. It is used during death animations to transition monsters from their normal blocking state to corpses that can be walked over.

Uses
The  code pointer appears in the following states in Doom's state table:

Example
The following is an example of how to set the  code pointer in a Dehacked file:

Pointer 21 (Frame 34) Codep Frame = 751

Or using BEX syntax:

[CODEPTR] Frame 1234 = Fall