The v-notch tool is used to cut a "V" in the tail of female lobsters found to be carrying eggs. This is the kind of tool used today. It is much faster than using a knife to cut the notch, although it does cost $16.00, something more than a knife. The notch usually lasts through several moltings or several seasons. It is illegal to catch and keep a lobster with a V-notch in it. This rule helps preserve the breeding stock of lobsters.