5. What is the name of the block that occupies 1/2 of a block, while the other half of the block is still empty? (They exist in several materials, including but not limited to stone, cobblestone, and different types of wooden planks.)
From Quiz Powers of 2 in "Minecraft"
Answer:
Slab
Slabs can be put on the bottom half or top half of a block. You can also put two of the same type in the same square, and it will look like a normal block of that material (except for stone). However, when you break it, you will get two slabs back, not the original block.
Stairs normally occupy 3/4 of a block (half of it is full height, while half of it is 1/2 height), pressure plates do not occupy any space, and doors, while they can be made of different types of wood, are thin and vertical, and cannot be made of stone or cobblestone.