Keep in mind that this is a pinned element installation. So we are going to screw into the soft brick only a short way, like an inch. The marinite board is 1/2" thick, the spacer is 1", so that leaves us with an inch of penetration into the soft brick. You really only need a tiny pilot hole and you do the final drilling and tightening down when you are sure you are ready. Just snug the marinite screws lightly. Then finish by attaching the element leads and power cord, etc.

The spacers can be any length (usually 1 or 2 inches). Joppa Glassworks, Inc. has a supply of small cordierite tubing that can be used for this purpose. $1.00 each.