The crates won't be glued, screwed, or held together any other way. Two crate towers on both sides of the bridge filled with bottles of water, a few meters high each and weighing in at 1.5 metric tons a piece, will hold together the construction the moment the supporting scaffolding is removed.
The bridge will span the Dommel River between Limbopad and the bicycle bridge. The location has its limitations, so it will be quite a challenge. For example, the students can't go into the water and they must handle the river banks with care to protect their flora and fauna.