Resawn Reclaimed Barn Wood Box Beam Fireplace MantelsReclaimed Resawn Barnwood Box Beam Fireplace Mantels An alternative to solid reclaimed barn wood mantels is by building a hollow box beam mantel. Doing so allows you far greater precision in the final mantel dimensions. A box beam fireplace mantel is lighter and easier to install as well. Consider a box beam mantel when tolerances of your installation are more exacting and where you need more control over the final look. We make box beam fireplace