what kind of fenders? are the fenders pre-drilled for the braces or do you need to drill holes (higher-end fenders are like this!)? Heavy weight, middle-weight, lightweight, other?
Front fenders are USUALLY mounted using 1 or 2 braces going to the axle or a mounting hole on the fork. Rears are the same...some mount to the axle, others use another mounting hole...the rears also (sometimes) have a tab for mounting them to the frame behind the bottom bracket (to the chainstay bridge)