They are a clever design, the shelves by themselves are quite weak, but as you assemble the system it gains its strength. Huh, maybe I did learn something about stress loading in college after all...
The shelves were a freebie, the shop my mum works in is closing down soon and as they slowly clear the stock they find themselves with spare sets of shelves. With any luck they will have a closing down sale again (not the first time the owner has said he is closing down), as I get my mums staff discount on top of sale discount... ebay heaven! Last time I filled the BMW to the roof 5 times! Another sale would pay for a full resto on Baby Bertha!