Step B: Attach the Trim
1. Cut the corner trim (C) to length. Overlap the edges of the corner trim pieces at the corner, forming a square butt joint. Fasten the corner trim pieces to the panels by driving 1 1/4" deck screws through the inside faces of the panels and into the corner pieces.
2. To provide extra support, drive screws or galvanized finish nails through the overlapping corner trim pieces and into the edges of the adjacent trim piece.
3. Cut the bottom trim pieces (D, E) to length. Fasten them to the end and side panels, between the corner trim pieces. Drive 1 1/4" deck screws through the side and end panels and into the bottom trim pieces.
4. Cut the top caps (F, G) to length. Cut 45° miters at both ends of one cap piece, using a miter box and back saw.
5. Tack the mitered cap piece to the top edge of the planter, with the outside edges flush with the outer edges of the corner trim pieces. For a proper fit, use this cap piece to guide the marking and cutting of the miters on the other cap pieces.
6. Miter both ends of each piece. Tack it to the box so it makes a square corner with the previously installed piece. If the corners don't fit just right, loosen the pieces, and adjust them until everything is square.
7. Permanently attach all the cap pieces to the box, using 6d galvanized finish nails.