"A" style mounting provides threaded holes in the body of the block. This can be found on all the square body (H) type blocks and some of the flange body (W) type blocks.

This is for top mounting using bolts passing through the item being attached to the block. Hole sizes vary depending on the size of the blocks, and you can get more specific information about this and recommended fastener sizes in the bearing tech pages for this site.

"B" style mounting provides smooth thru-holes in the body of the block. This can be found on many of the flange body (W) type blocks.

This is for bottom mounting using bolts passing through the underneath side of the block and threaded into or passing through the item being secured to the block. You can get more specific information about hole sizes and recommended fasteners in the various bearing tech pages in this site.

"C" style mounting is found on some W type blocks, and it provides the versatility of mounting either from the top or the bottom.

In this style, each hole is tapped near the top of the block, but there is also a counterbore on the bottom. Thus, a cap screw can be passed through the work and secured directly into the block from the top. Alternately, a slightly smaller cap screw can be inserted from the bottom through the hole to secure the work from this direction.

You can get more specific information about hole sizes and recommended fasteners in the various bearing tech pages in this site.