Two and a Half Inch Rule
The Two and One Half Inch Rule is an important rule for weapon building and checking. Put simply, no part of a striking surface of any weapon can go more than half an inch through a 2.5" hole. The main purpose of the rule is to make it difficult for weapons to make significant contact with the eye. The only exceptions are swords with a 1.5" radius semi-circular tip.
1.3.3. Two and one-half inch rule—No surface on a striking edge (sword tip, arrow head, spear head, javelin head, etc.) whether designed for stabbing or not, may pass more than 0.5 inch through a 2.5 inch hole; swords with a semicircular tip, with a minimum 1.5 inch radius are exempt from this rule.