Here are some photos of a P & H Bows (London), it's the one with a plastic frog. I have seen lots of these and they are fairly easy to get apart and then rehair. There is a small hole at the back of the slide where you can put the bow screw into and push it out. When I rehair one of these bows, I don't use their method. First you need to get rid of the built in wedge and fill in the tip so you can fit a normal block.<http://b.cs-violin-shop.com/p>
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They also have a carbon fiber model with an ebony frog. It's not obvious, but the frog comes apart in the same way as the plastic model and the hole in the slide is near the ring.
So far I have only rehaired one of the carbon fiber bows and it was quite a pain. The slide was stuck and would not budge. I injected steam under the slide thinking it was glued in. The problem ended up being that the rear plate was too tight in the frog, perhaps the ebony shrunk a little. To get it back together I needed to file the back plate so it would fit back into the frog. Didn't take any pictures of that one.
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Why do some people put the hair under the block?
Here is an unusual screw, notice the way the end of the screw was formed.