S-Bolts are a convenient way of mounting trucks easily. The bridge avoids the bolts from spinning so you only have to use one hand to attach your truck. With its flat profile, it protects your board by not widening the mounting holes and is non-intrusive so you don't feel them when you are skating.
 
1.5" fits perfectly for the Platypusher with 90mm wheels and 1/4" riser. I also use 1.5" bolts for mounting the TTX or S Tail to the Procyon.
 
Comes in sets of 4 S-bolts.