Bandbox selection
Ctrl+alt+lmb-drag allows you to drag out a bandbox, highly useful for selecting a bunch of things at once
 Vetex editing
Vertex editing is one of the best tools of unrealed when working with bsp, to activate it click on the vertex editing mode icon (top right of the toolbar) Once you are in vertex editing mode you can control+click or ctrl+alt+lmb-drag to select vertices, you can then move them around with ctrl+lmb-drag. This is not as error prone as you may think, but there are 2 big ways to make bsp holes. Don't overlap vertices If you do this one of the following will happen:
- Your vertices will stick together.
- You will get a bruih that has BSP errors.
- You will get a GPF and your editor will crash.
 Dont make your brush "inside out"
I discovered this one the hard way . If you drag your brush through itself (i.e. drag the bottom vertices of a cube out through the top) your brush will invert and actually affect the area outside of it, so if you subtract, you delete everything outside your brush and vice versa.
 Use the groups browser!
While it may seem useless when you just start out, once your map begins to fill with static meshes you'll wish that you could make all of your wall panels in a section hidden, or select a whole bunch of lights to shrink their corona with a click of a button, use the groups browser, you wont regret it.
- Open the groups browser the 'G' icon along with your textures, static meshes, animations, etc..
- To add a group click the new group button (looks like a page) give it a name
- To add items to a group select your items and the group and then click the add to group button(has a +)
- To remove items from a group select your items and the group and then click the remove from group button(has a -)
- To select/Deselect a group click the select/deselect icons(red boxes). any other objects you had selected will remain selected
- To hide/show a group click the checkbox beside it's name
 Create atmosphere!
Atmosphere is the most important thing to think about while making a map. In short terms, the atmosphere is the 'mood' of the area. If you had a dark, foggy area in your map, it would give off a scary, horror like atmosphere. When mapping for Killing Floor, or any game for that matter, you can create atmosphere in a variety of ways. Great ways to do so are with Ambient Sounds. Killing Floor comes with a huge amount of various sounds that you can use in your maps, from water leaking, wood creaking, to moans in the distance. These can help build suspense in your map.
Sounds aren't the only way to give your map an atmosphere to fit your needs; clever use of lighting can as well. Not every place needs to have several light bulbs to light up the area. You could light up an old manor house with a single orange fire resting in a fire place. Mixing and matching different colour lights within the SDK can also give it a better atmosphere. Blue lights could be given off glow sticks lying on the floor next to a corpse, or red lights could be pulsing off an emergency warning light.
Lighting and sounds aren't the only way to add to the atmosphere and tension. If you're making a single player, or a mission map, where you won't continuously encounter specimens, you should stop in-game music playing to create more suspense for when the player does encounter specimens.
Another very important thing to remember while mapping is, if you're creating a scary atmosphere, say, in an abandoned train station, the place of course is abandoned. Players shouldn't expect to see perfectly clean floors, upright furniture and working lights. Tilting that extra static mesh can greatly improve the atmosphere of your map.
 See also
SDK For known bugs.