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Home Depot sells a small spring clamp that is perfect. I like them because you can tweak the shape with a pair of needle nosed pliers so that they fit kerfing better. Only takes seconds per clamp to fix them and I have been using them for many years without any loss of clamping force. They were about 50 cents a piece when I bought them, but probably are more now. Way better than clothes pins with rubber bands, which I used for more than 30 years .-Bob

I've been using clamps that look like the ones John mentions or ones that look like them. I wound up with two batches, the older ones clamped much harder than the second batch, but even the weaker ones did the job.