Which options are you missing?
Viewing post in Respect The Horde (Demo) comments
The pitch is that you're creating paths for the zombies to run into environmental hazards but it's pretty tough to path them out with just the two types of wall and limited scrap available, and if you find the level item close to their spawn point or backed up in a corner you're kind of screwed in advance because they spawn so quickly that you don't have a chance to use that to your advantage. When manipulating the horde works it's fun but with my time in it that only happened maybe once so far.