When using the 1 ½” tall aluminum bracket and installing in a brick wall, you have to drill a hole into the grout line and insert a dowel (preferably with some Pl or epoxy)
If the brick are solid bricks you may use a so called Tapcon (blue) and drill directly into the brick. (The holding strength is inferior)
When using the steel bracket, you absolutely must drill a hole into the grout line and use expansion bolts. Using 2-component epoxy or PL or Hilti glue will increase the holding strength dramatically.
Note that using the aluminum bracket on brick wall is not the ideal.
For brick walls we need to use expansion bolts in the grout line. (never in the brick itself as it will crumble and not hold anything, because often bricks are mostly hollow)
Most expansion bolts are too large – especially the head, since it is a nut – see picture, to fit into the aluminum bracket. This is why we usually use the steel bracket when attaching something (fireplace mantel) on to the brick wall.
You can use the aluminum bracket, but then you will have to use a normal plastic dowel with a corresponding screw (still needs to be a flat head). But note that this will not hold a fireplace mantel.
The only other way is to attach a 2 x 4 with expansion bolts on to the brick wall, (the nut has to be recessed into the 2 x 4) in order to create a flat surface onto which you can now attach the male bracket to. But this defies the whole purpose.
People often think to save money on the aluminum bracket rather than the steel to hold a heavy fireplace mantel. In theory, it's a great idea, but in practice the anchors needed to attach the male bracket to the brick wall have to be so large and sturdy that they are too big to fit into the aluminum bracket - thus defeating the purpose.
