If installing "newer" thru-hulls, you can also use valves and other pipe fittings that have tapered threads because these "newer" bronze thru-hulls, at least those manufactured by Perko and Groco, among others, are manufactured with the last 2-3 threads tapered. This taper allows fittings with tapered threads to screw on for a full 5 turns, providing the joint with maximum strength, unlike the 2-3 threads that an all-straight threaded thru-hull allows. These tapered threaded thru-hulls can still be used with seacocks, fittings which have all-straight threads. Now for the better part. If you are working with the "older" all straight threaded thru-hulls, you can convert them to having the last 2-3 threads tapered just by using a tapered pipe die on them, a large enough wrench, and a little bit of muscle. Just make sure to match size and pitch. At least that's what Jill says after having just done so on a recent job. Rudy & Jill Sechez Jacksonville, Fl BRINEY BUG-a 34' Sail-Assisted Trawler 850-832-7748 *TRAWLER TRAINING & ANCHORING CONSULTANTS"ANCHORING-A Ground Tackler's Apprentice" (E-book or Hard Copy)*