Please help us in explaining the regrab glitch here.
Regrab Glitch is a technique used in SOMA and Amnesia: Rebirth which allows the player to clip out of bounds and/or prop fly with the lift-able object the player is grabbing.
In the game, when the player grabs and holds onto an object, the game is designed to disable the collision of the object with the player model. This prevents you from being able to fly by holding onto an object you are standing on and staying in the air. However, in SOMA and Amnesia: Rebirth, if you hold an object such that it intersects with your player model, let go, and re-grab onto it quickly while it is still inside your player model, the object will re-gain collision with your player model. The physics engine will then push your player model out of the object in the most direct manner such that they are no longer intersecting, and afterwards your player model will still collide with the object as long as you are holding it.
The push after regrabbing the object can be used to clip through walls. If the closest path to push you out of the object is in the same direction as a wall, then you will be given some push force against the wall. If the wall is thin enough, you can be pushed all the way through the wall.
After the object regains collision with you, you can stand on it and fly by jumping while holding the object underneath you.