What is "case knives"

Usage examples of "case knives".

During the night quite a number of the boys, who had fabricated little saws out of case knives and fragments of hoop iron, cut holes through the bottoms of the cars, through which they dropped to the ground and escaped, but were mostly recaptured after several days.

I can personally vouch for the advantages of that, with specific regard to the ensuing lack of men with guns - or in this case knives - visiting your house later on.