What is the T-shaped bracket on the side of the T-29, T-30 and others?

The_Chieftain: It's a general purpose stowage rack, though usually the tarpaulin or camo netting would go in it. One photo shows bedrolls and helmets draped on it. If done right, the crews should be able to create a waterproof burrito of the tarp with the interior being things like the backpacks/personal gear which they want to keep dry.   M26 and M46 had such racks, you can see them being used in the field if you look up photos of them from Korea.