Use the wooden blocks to build a bridge. Holding on to the hand rail, see if the bridge will bear your weight.
It's all about the arch shape of a bridge; the arch is a very strong shape. If force is applied from above, the force pressing down spreads along the line of bricks, pushing them together to the take the weight. Applying a force from a different direction has a very different result.
Can you really make a bridge from paper that a car can drive over?
Try crushing an egg by holding it at the top and bottom. Its very hard to do. This is because like arch bridges, eggs spread out forces that are put on them. They are strongest at the top and bottom, if this didn't happen chickens wouldn't be able to sit on them.
Physics in action in the building of a vaulted ceiling - from hand!
Arch Bridge Visitor Sheet