How to cut a brick wall opening
Have the plywood cut to size (we cut ours to 1800mm wide x 1200mm high). Set up a mitre saw with a stopper to cut lengths of dowel in half, cutting three lengths at a time. Note the dowel is slightly longer than 2.4m, which allows for the width of the saw blade.
Tip: Using 12mm-thick plywood as the backing for the dowel keeps it lightweight so it can be constructed on a flat surface, then moved and attached to a wall using fast-drying construction adhesive.
Position a long side of the plywood against a wall to use it as a straightedge. Apply woodworking adhesive along the back of the first piece of dowel, then position it flush with the edge of the plywood. Use the nail gun to pin it in four places, about 75mm from the ends and 350mm apart. To ensure the nails are almost invisible, avoid nailing through the middle of the dowel. Instead, position the gun to the side of the dowel, about a third of the way up, to shoot into the plywood on alternating sides of the dowel.
Add woodworking adhesive to the next piece of dowel and position it against the first, making sure the long side of the plywood is straight against the wall and the ends of the dowel are even. Secure using the nail gun and repeat to finish the wall, wiping away excess adhesive with a clean, damp cloth as you go.
To frame along the top, cut the moulding to the same length, apply woodworking adhesive, then use the nail gun to attach it along the top, securing nails about 300mm apart and angling them to go through the end-grain of the dowel pieces. Wipe away excess adhesive with a damp cloth.
Smooth over all the nails with timber filler using a flexible steel blade, leaving to dry. Smooth with 180-grit abrasive paper, holding the sanding block at an angle between the dowel, then clean away dust with a damp cloth. Seal with two coats of varnish using a mini roller, wiping away excess with a clean cloth.
Ensure the wall is clean and free of dust. On the back of the plywood, use a caulking gun to apply construction adhesive in a zigzag pattern for maximum coverage. Position it against the wall then pull it away, leave to dry for maximum five minutes, then reposition against the wall and apply pressure as it cures.