The pre-drilled holes on each side are given a healthy bubble of wood glue and six dowels are inserted 3" deep into one plank.
With a hammer, the two sides are tapped gently together. If much force needs to be applied, it is best to use another block of wood as a beater to avoid marring the edges of the finished piece.
In a few hours the two sides of the doweled step stool will be firmly fixed in place.
Full curing time depends on the wood glue used, but usually takes 24 - 48 hours. I like the results: a simple sturdy child's step stool or comfy adult bench. If I can work out some of the kinks, a prettified version should be on sale soon -you know where - Hip Thrift.
And in completely unrelated news, this mess blessed me in front of my house in the morning . . .
What madness can I contrive from a broken exercise bike? The future remains unknown, though I certainly had a good time disassembling it!