Prefinished siding and trim – whether fiber-cement, plastic, or wood – are becoming more popular. Factory-applied finishes are hard to beat, and it's great not to have to schedule another sub or deal with weather-related painting delays. For the best look, matching color-coated nails should be used, and care must be taken to protect both the heads of these nails and the adjacent material surface. We found polyurethane Protect-O-Cap hammer caps at the request of one of our testers and gave him some to test. Here are his results.

Fitting these caps to your favorite trim hammer might be a challenge. I prefer trimming with my 16-ounce curved claw hammer, but the caps don't fit tightly enough over its face. Even with the provided shim sleeve installed, a cap will skew, loosen, and pop off unless I shim it on with soft flashing tape and wrap it securely with nonmarking white electrical tape. I found tight fits with an Estwing 20-ounce rip claw hammer and an older Stiletto 14-ounce model. Heating up the plastic parts helped ease a very snug fit; otherwise, the plastic shim sleeves sometimes split when pounded over the hammer face.

Once in action, I was glad to discover that the Protect-O-Caps work. However, I was not impressed with their longevity, especially for those of us who hit pretty much dead center all the time. Although they do a good job of maintaining the paint coating on the nail heads, they become a real pain if not replaced soon enough. The polyurethane material softens and turns into hamburger quickly, at which point the nail heads sink into the caps and stick. Hitting a knot can also ruin a cap.

For pounding nails, Protect-O-Caps should be treated as a short-term consumable accessory like a utility knife blade or a drywaller's screw-gun bit. Expect anything more and you'll be disappointed. Three of us went through about 18 caps while trimming a complex 3,300-square-foot house, driving about 20 pounds of 2- and 2-1/2-inch nails. But for nonnailing uses, where a cap on your hammer would take the place of a nonmarring mallet, Protect-O-Caps would probably last a long time.

The plastic caps absorb a lot of the hammer's impact energy, so it takes six to eight blows to sink a nail that three to four hits would sink with a bare metal face. We drive the last 1/8 inch with a flat drift punch – just one tap – which doesn't take the paint off.

The Verdict

Even though they proved to be less durable than I'd hoped, I'm probably going to keep using Protect-O-Caps, because the end result is exactly what I envisioned: unmarred white nails driven flush to a white finished surface. The caps do the job, but I can't help wondering if a higher-durometer plastic would work even better by lasting longer. Also, offering spacer sleeves of various thicknesses – to allow the caps to fit a wider variety of favorite hammers – would be a nice option.

John Spier owns Spier Construction on Block Island, R.I.

Trim Hammer Cap
PRICE: $2 each in multiple packs