The game has a couple special tags to help with mapping

The penetrable tag allows for anything that has the tag to be shot through, can go through up to 32 things. Useful for situations where you might have a thin wall or weak cover like a piece of plywood. Should be used sparingly.

To apply simply add the tag to anything like a prop_static or func_brush. Make sure you click the green plus button to add the tag.

Should look like below when applied:

The corpse tag is a special tag that automatically applies to dead bodies. This is useful to set up triggers that only activate with bodies for things like objectives or body destroyers.

To use create a trigger_multiple or trigger_once and add the corpse tag to Activation Tags and remove the player tag.

Should look like below when applied.

corpse - for corpse only on trigger

debris

carriable - only equipment