I'm very confused about the Boolean difference modifier. I'm modelling a concrete road block for use in a board game. I've created a basic shape and now I want to create grooves in the side by subtracting a wedge using the Boolean modifier. I have uploaded my Blender file to Google Drive:
I've got two copies of my roadblock, named Roadblock 1 and Roadblock 2. The shape I want to subtract is named Wedge. Here's a screenshot (I'm working on one of the copies of the roadblock):
When I select the wedge in the modifier's "Object" field, the roadblock shape disappears completely. I can't put any additional pictures, my reputation isn't high enough. I have tried this with both roadblock objects, and both have the same problem. No matter where I try to subtract the wedge from the object, it disappears entirely. To find out it was the roadblock or the wedge that caused the problem, added a cube and tried subtracting the wedge from the cube, this worked normally. I'm a complete beginner at Blender, and I find this very confusing.