How do I attach vertical mantel support beams to wall?

[Nick2cd]

A friend asked me to build a mantel surround for his fireplace. I'm considering something pretty traditional with two vertical support beams and a mantle trimmed out in crown moulding.  I plan to build the vertical beams from either plywood or 1x material (essentially they will be long shallow boxes).  I don't want to build the mantle at his house, I would prefer to build in my shop. So, how do I attach the vertical beams to the wall, yet still hide the fasteners?  Not sure if this will come across clearly.

 

[rnt80]

If I'm understanding you correctly I would attach a plywood cleat to the wall and then brad nail the box to that from the side.  Hope that makes sense.

 

[peter halle]

I'll also throw in that a mantle offers lots of possibilities for the covering of fastener locations with additional layers or moldings.  You don't have to go wild, but they are there.  Smaller moldings are also great at where your mantle will meet the wall to hide or partially hide gaps.

Peter

 

[Brent Taylor]

I have used 2x material with a french cleat for the mantel support and 1x or 2x for the uprights. A couple of brads or finish screws and your done. But be sure to solidly anchor everything, people are stupid by nature. B