Cleanup is going to take awhile, so the site is back up but editing has been disabled.

From HalfLife 2 Knowledge Base

This tutorial explains how to make a Basic Ladder using the entity func_ladder. I'm assuming you already know how to make brushes and most of the basics. If not go and read the following tutorial, First CSS Room.

Steps

1. Step one is to make a brush with the dimensions you want your ladder to be. I made mine about 28 units wide and 4 units deep, the height can be whatever you need.

2. The brush will probably look pretty ugly without a nice ladder texture applied so let's give it one. Select the brush you have just created by left clicking on it. Now open the Texture Application Tool, you can do this by clicking on the multi-coloured cube in the toolbar on the left. A window will open, select the browse button, now you are presented with the Texture Browse Window. Type "ladder" in the box down the bottom marked "Filter", this narrows the textures displayed down to the ones with the word "ladder" in thier name. Double-Click the texture named "metal/metalladder001a" and the Texture Browse Window should close.

3. Click the Apply button in the Texture Application Tool's window. The texture won't match the ladder so we need to adjust it. In the two boxes under "Texture scale" enter the number 0.30 Now we need to adjust the position of the texture, In the Box marked "X" under "Texture shift" enter the number 23. Leave the box marked Y on 0. Click the apply Button again and the texture should be all lined up properly. Close the Texture Application Tool.

4. With the ladder brush still selected, right click on it in one of the 2d views and select "Tie to Entity", in the window that appears select func_ladder in the box under "Class". Now click apply and close it.

For the people who think this tutorial is wrong

A lot of Half-Life 1 and CS Mappers are now probably screaming out "You can't do that n00b!"
To that I say this: Changes have been made to the func_ladder entity and there is no aaatrigger texture any more, so this IS how you make a ladder for source.

There are other people who are going to mention using the "toolsinvisibleladder" texture in place of the aaatrigger texture.
To that I say this: That makes the brush with the ladder texture behind it invisible and it's for people who want to make a wall which can be climbed on.