Step 10:

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Now just assemble the four peaces together. I just used long screws and some wood glue.

Ta-Da, a sturdy planter.

I do not have a bottom on mine, because I am filling it up with good dirt and letting the roots of the plants just work their way down. You can put a bottom on it easily enough, however.

This way is a lot easier than trying to get those impossible nails out of the pallets.
Excellent instructable. Having no circular saw, I was glad to see the hammer and claw alternative to the remaining nails. I've been looking into an improvement for my container gardens - this is a great jumping-off point for a cold frame. Thanks again for sharing!