Question

What real life object could a triangular prism be used for

Answer 1

We can start out simple, so here's some:

If you ever drew a sea saw as a child, or seen it, you probably had seen a part that looks like a triangular prism. It's somewhere in the structure.

Many building infrastructures have them. The roofs of many houses are pointed in some what of a triangle like shape so that rain water can roll off of them easier.

Hope these two help or at least spark some ideas!