Placing the ladder model

Click on the Entity Creation Tool and select "prop_static" from the Objects drop-down menu on the Entity Box if it isn't already set as this.

Place a prop_static by clicking near the wall that you want to place the ladder on.

Deselect the prop_static by pressing the Esc Key then double-click on it to bring up its properties.

Click on the World Model row.

Click on the Browse Button on the right of the Object Properties dialogue box.

Type "ladder" into the Filter field.

Select props_c17/metalladder002.mdl and click on the OK Button

You should now have the ladder where you placed your prop_static

Rotate and move your ladder so that it is in the middle of this back wall and the bottom touches the floor

Creating a func_ladder

Now that you have the model that shows where your ladder is, you will need to place the actual entity that allows players and npc's to climb it.

Making the tools/toolsnodraw texture the current texture.

Click on the Browse Button on the Texture Box.

Type "nodraw" into the filter.

Double-click on the texture "tools/toolsnodraw"

Decrease your grid size to fit the ladder better by pressing the [ key twice.

Click on the 5^th icon on the Tool Bar (the Block Creation Tool) and then draw a brush in the Top viewport in front of the ladder.

Now, you will need to make one face of the brush (the face that points out from the ladder) a ladder texture. To edit individual faces of brushes, click on the 6^th icon on the Tool Bar, the Texture application mode button

You will see the Face Edit Sheet dialog box appear

With this dialog box still appearing, select the face pointing away from the ladder in the Camera viewport with the left mouse button.

Click on the Browse Button in the Face Edit Sheet dialog box and you will see the Textures window appear again.

Type "ladder" into the Filter field.

Double-click the texture "tools/toolsinvisibleladder".

You should see the LADDER texture now occupying the thumbnail in the Face Edit Sheet.

Now click the Apply Button and your selected face should change to the LADDER texture.

Exit the Texture application mode by closing the Face Edit Sheet dialog box.

Select the brush with the LADDER texture on the one face.

Go to Tools > Tie to Entity

This will make the brush a Brush Entity. The default brush entity is a func_detail which we will talk about this another tutorial

We want to make this brush entity a func_ladder. Pull down the drop-down menu choices and select "func_ladder".

Then click on the Apply Button.

Close the Object Properties dialog box and then save your level

Now compile the level by pressing the F9 Key and then clicking on the OK Button.

You should see your ladder look something like this:

Setting up the nav meshes for the ladder

In order for the other AI to use the ladder you will need to set-up the nav meshing for the ladder.

To create a nav on a func_ladder, type sv_cheats into the console then nav_edit 1, position your cursor over the ladder and type nav_build_ladder, this should create a nav mesh for the ladder.

Note: The cursor will turn a green colour if it is positioned over a func_ladder. 

For more information on setting up nav meshes, see Here

That's It for this tutorial, hope it helps

Welshy