The picture show two types of side bracket brace. The lower side bracket has only one fitted brace at the top. A matching brace was made to fit the bottom of the bracket as well. The braces were added for extra strength. This was especially true for horizontal stresses created when the line wire changed direction. If the wire turned inward (toward the pole) a brace woud be installed at the lower portion of the bracket. If the wire turned outward (away from the pole) the brace would be installed at the top of the bracket. The braces were usually installed in a position over the mounting nails for the bracket. after the bracket was nailed in place. In the upper example the brace has a hole that allows the brace to be installed at the time the bracket is installed.