This product comes in a small plastic container, and is a liquid that they say is thinner than water, will penetrate all the small cracks, but then hardens and seal them. Most chandleries have it, including West Marine and others. Cost about $12.00 or so.
I use it annually on the toe rail, all
cleats and other deck fittings, around the windows, etc. to ensure that no leaks develop.
Frank.