jointswoodwoodworking
What's the best way to attach a board to another board that's resting over it?
The rail is a 2×4 and it will be held, on each side, by a 4×4. Under the 2×4 rail I'll have another 2×4 that will keep the top 2×4 straight.
This is basically it:
I only have a circular saw and a jigsaw, so, I can't do complex joints.
I forgot to mention that I have to attach these 2x4s to the 4×4 wood posts.
Toenailing through the baluster on the uphill side with a finishing nail gun should be quite sufficient. The plowed channel holds them laterally. If you wanted extra strength, you could add glue just before nailing.
16 or 18 gauge nails about 1 inch to 1 1/4 long should suffice. The hole will likely be nearly invisible.
Additionally, plowed railings usually come with a filler strip that is angle cut to sit between the balusters after they are attached. If you use the nailing gun (and glue if you wish) to attach those as well, they would further lock in the baluster.
You have a few options available to you, based on the material which you find.
Provided that I understand how you want to assemble the structure you can do the following.
(see pics below)
Best Answer
Glue and Screw
Drill pilot holes from the bottom side of the lower 2x4 all the way through, Clamp the lower 2x4 in place and use 4 inch deck screws to screw up through the pilot holes and into the bottom of the upper 2x4 . ( 2x4 are only 3 1/2 inches ) so a 4 inch screw will give you enough thread to bite into the upper board just be careful not to drive them to far.
Screwing from the bottom this way will keep all screw heads hidden on the bottom side.
Apply OUTDOOR rated glue. Remove clamps.