The black and white swap that is going on now "rules":
The blocks must be 12 1/2" unfinished size.
Only black and white, no other colors.
Can be any fabric pattern in 100% cotton, pre-washed.
Can be any block pattern you want but it was decided not applique.
You make 12 blocks all the same.
Send them in and you get 1 of your blocks back and 11 other blocks, all different, to put together into a sampler quilt of your own.
You can still join the black and white swap. The blocks need to be sent in by June 1st.
Other swaps might have other rules. There was one recently where the blocks had to be blue and white stars.