ladders.wad 
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Effect demonstrated: - Ladders
A) Make a platform in your map of a height of around 112. Give one of the lines an appropriate texture for a ladder.
B) Place a two-sided linedef on the map, just in front of the line with the ladder texture. Don't give it any textures so it stays invisible to the player. Make sure the line is two-sided and that it's not set to impassable or block player in your editor.
Give this line a type of 454, which corresponds to our custom Ladder of 128 high in Lines.ddf
This is the code for the custom Ladder line:
[454] //ladder
TYPE=WALK;
ACTIVATORS=PLAYER;
LADDER.HEIGHT = 128;
Now when we press "UP" standing on top of this line we will start to climb.
