Two types are listed, on mulching(134149) and one hi-lift(138498.) These have the star hole in the center.
Please provide the model number when asking a question like this. Different models use different techniques. Craftsman LT1200
Husqvarna
Check your shear pins.
A person can get an owner's manual for a Craftsman lawn tractor by contacting the Craftsman company. The phone for customer service is 1-888-331-4569.
1997
MTD
1997
2006
There are two blades on that model. It has mixed reviews due to placement of some features but it is attractive to some people because of the large mower deck.
Try searspartsdirect.com
Most blade bolts on lawn mowers are reverse threaded. The bolts on the Craftsman brand lawn mower are also reversed.
Gates