The cooper used a croze to cut a groove into the bucket or barrel so the lid or bottom would fit securely against the wood. The cooper had to make sure the pieces of wood fit tightly together so none of the contents, such as milk or grain, would seep out.

Croze
Bibliographic Information:
Croze, 19th Century, wood & metal, H:5 X W: 13 x D 3 in. The Farmers’ Museum, Cooperstown, New York, F0039.1962.