Tutorial originally created by Wolf359 and posted to EFModCentral. Mirrored here for archival purposes. I've also mirrored his example map here.
We will start with a very basic room. Just 4 walls, a floor & a ceiling. To this we will add another floor halfway
to the ceiling. I'm sure you all know how to do this.
As it stands we cannot reach this new floor. This is where ladders come in.
First using the engineering/chrome texture (but any solid texture will do) we will build the basic ladder shape that we will see in the game itself.
This is just done with two tall brushes for the sides and several smaller brushes forming the rungs. This is just done so that we are able see what looks like a ladder in the game, it isn't necessary, we could have just made one solid brush that went to the second floor and this would have worked just as well.
OK. We now have the basic ladder but it is not climbable in the game yet.
What we need to do now is to pick the common/ladder texture from the textures list and make a new brush directly in front of our "ladder".
This brush must touch the floor and be wide & deep enough for the "bounding box" of the player to fit inside.
That's it we can now compile the map using the fullvis option and we will then be able to test it in the game.
This is the finished article. It is as easy as that.