If your wanting to Make a slidy door then you picked the right place to come, often used in sci-fi maps and anyway a slidy door may be, you can have the door slide right,left,up,down and all sorts.

Once you have your door shape made, and I trust you have the texture aligned correctly, then you can turn it into a door. "right click" your object when its highlighted, and then select "tie to entity" now select "func_door". Leave all the properties such as render fx, but do set your fx amount to 255, otherwise it will be invisible.

There are all sorts of properties to choose from, all self-explanatory really, one that you may wonder about is "lip" this is the amount that will stick out, say your door is going up, then you want it sticking down say 2 units, so put in 2, otherwise it will look odd.

Up, Down, Left or Right?

Now we want to choose which way the door is to slide, use the top view to do doors, if you want it to move right, then move the black arrow thing in relation to the door in top view like this:

There we are see, the door will move the way of the arrow, if you want the door to move up or down, then select up or down from the angle menu, which is next to the black circle on the picture there. Once your done, just get the screen off, and go test your door, if anything has gone wrong, it'll be the direction the door went :P but it should be fine :)

You can download the room, hall, door and glass tutorial map pack here, it includes the .bsp files and the .rmf files N/A