The HPL2 Level Editor is a prop heavy level designer. About 90% of your map will consist of prop Walls, Ceilings, and Doorways. Props also make up details such as windows, furniture, debris, etc… I will talk about that later on.
Props are created by selecting the Static Objects tool(6) and some with the Entity Tool (7). Both tools do not use the same props, Static Objects is used for props that are used to create the map, such as Walls, Ceilings, Doorways(not doors), Debris with physics(Rocks, Carpets).
The Entity Tool is used for props you can interact and Script with. Props such as Doors, Closets and chests that open, tinderboxes/oil, NPC, interactive items, notes and diary entries. Think dynamic with entities, they are the props that are used in scripting and events. Entities would be something like a key that opens a door, or a door that loads a new map. Entities are Props that can or do serve a purpose, think physics, furniture, inventory items, quest items, levers, doors, torches, etc…