Commented 10 months ago2019-11-19 17:29:13 UTC in wiki page: Tutorial: Ladders Comment #102435
You can create toggleable ladders by changing func_doors' content type (empty, water, lava, etc. func_water is basically a func_door with water contents). Adding the key "skin" with the value of "-16" by turning smart edit off, you change the door's content to ladder. This makes a moving ladder (like how raising water works) but since doors weren't supposed to be used like that, the ladder behaves strangely in it's open position. You can create two very fast func_doors at where the open and closed positions of the ladder is supposed to be and make them open to inside a wall (or anywhere the player can't reach), then create a fake ladder by creating another func_door without the "skin" key to circumvent this problem.

You can also try changing the contents of a func_illusionary.