Planter Boxes with French Cleat hangers
Use 16mm plywood to make planter boxes mounted on a French cleat system that allows you to easily remove the planter boxes when necessary.
A French cleat is a great way to hang heavy items. It's also a system where you can hang items and easily remove them when you need to.
For planter boxes, where a French cleat mounting is used, you can easily lift the boxes off the hanger to water or replace the plants.
YOU WILL NEED:
1 of 32 x 67 x 1800mm pine - French cleats / mounting plank (1200mm long)
3 of 16 x 150 x 150mm plywood - sides and back
1 of 16 x 166 x 182mm plywood - front
1 of 16 x 182 x 182mm plywood - back
3.5 x 30mm screws
Exterior wood glue
Cup hooks 
Optional: Rust-Oleum Ultimate Wood Stain
Drill / Driver plus assorted bits
Mitre saw or table saw - or mitre box and backsaw
Tape measure and pencil
Buy everything you need for this project at Builders Warehouse.
1. The integral part of this system is the French cleat, and to make a French cleat you need to use a compound mitre saw. The compound angle is 45-degrees.
GOOD TO KNOW: You could use a mitre box and backsaw, but be prepared to put in some effort to cut the angles using this method.
GOOD TO KNOW: Cut the  French cleats from a long, single plank, so that you are always working well away from the blade.
2. Use wood glue and 30mm screws to attach one half of the French cleat to the box back, as shown.
3. Assemble the boxes by gluing the sides, front and back onto the base. Clamp and leave overnight.
4. Drill 4mm holes through the base to allow water to flow through.
5. Along the 1200mm long mounting plank make a mark at 20mm, 346mm, 672mm and 998mm. Of the 4 cleats you need to attach to the plank, take two and pair them up to mark the position for mounting the bottom half of the cleat to the plank. Using the previous marks as a guide, place the pair on the board and mark the bottom of the cleat to indicate where to attach.
6. Secure the bottom cleat on the plank with 30mm screws - drive through the back of the mounting plank.
7. If you want the planter boxes to last longer, you need to offer some protection from water. I applied 2 coats of Rust-Oleum LeakSeal inside the boxes. This flexible rubber coating repels water, and although not completely waterproof, the boxes will last far longer than if left untreated.
8. To hang the planter boxes on a wall, add a couple of cup hooks at the top of the plank - on the sides. The finished project will be quite heavy once the plants are potted up, and I think the two hooks should be enough to hold everything.
I chose the finish of the planter boxes with Rust-Oleum Ultimate Wood Stain in rustic sage. You can stain, seal or paint the boxes in your desired finish, or simply let them age naturally. Rust-Oleum also offer a Soft-Touch Polyurethane and Ultimate Spar Varnish that can be applied over the wood stain.