An example of the effect achieved by using "No collide world" on a train in Garry's Mod 13, gm_flatgrass
No Collide World is a custom tool in Garry's Mod.
Function
No Collide World removes collision with the world, in a similar fasion to the normal No Collide Tool.
This tool allows the user to place items through the world, which includes placing items through the floor