My chickens love spilling their chicken grit all over the coop. It attaches using a cable tie, or elastic band. 

The chickens love it and, so far, haven't pecked it to death. We have three chickens and it's the right size and capacity for them, but in all honesty, it's probably good for quite a few more birds. 

There are two versions:

1- Very simple, works fine, but a little fiddly when filling up.

2- One with an additional lip to reduce spillage when filling it up.