Are book plate holders good to use for wet plates?

Book style plate holders have metal insides. They have tiny bits of metal that spin on screws to hold glass in. I've always assumed that they were made for dry plates. They are double sided.
Could they be used for wet plate photography?

Yes they can be used but make sure you varnish any exposed metal because silver nitrate will eat it up. A good coat of varnish on everything inside the holder is a good idea because of the silver nitrate dripping onto the wooden parts of the holder also.