Shelving Stuff Ups

It seems to be a case of all brawn and no brain. The people responsible for putting the shelves back into place after the carpet laying at the library have become worse and worse at the job the further they progress through the library. The teen book shelves were a complete muddle this morning. The shelving units weren't in the correct position, the individual shelves weren't in the correct slots, shelves weren't aligned and the books weren't even in alphabetical order. How hard is A,B,C? Why would you place books upside down and back to front? I'm not sure if the workers are stupid, lazy, careless or all three.