An assembly includes a first bracket and a second bracket. The first bracket includes a first member that includes a plurality of fingers and a first channel between the plurality of fingers. The first channel includes a plurality of teeth. A first flange extends from the first member and includes a first engagement surface. The second bracket includes a second member and a third member spaced from the second member. A second channel is formed between the second member and the third member. A second flange extends from the second member on an opposite side of the second member from the third member. The second flange includes a second engagement surface. In an installed configuration, the first bracket is secured to the second bracket; the first engagement surface faces the second engagement surface; and the plurality of fingers are inserted into the second channel.