How to Repair Torn-Out Canvas Snaps, Fasteners and Zippers

To undo a tight snap, slide a finger under the fabric and pull straight up on the snap itself, or use a snap-release tool. Don't peel the canvas away. If a snap is crusted with salt, rinse it with fresh water, work in a snap lubricant (Boating Magazine suggests even a wax crayon or candle works), and wait a minute before trying again.

Canvas shrinks in cold. Put covers and enclosures on when they're warm (a sunny afternoon), or warm the fabric a little in the sun first. Never use a heat gun on canvas or clear vinyl. If a snap still won't reach after the canvas is warm, a snap extender (a short strap with a snap at each end) or a new stud placed slightly closer is better than forcing it.

• Clean pull-out, fabric intact: you can usually set a new snap in the same place or right next to it.
• Torn or frayed hole: you need a patch on the underside first.
• Long tear, rotten fabric or a seam failure: this is a canvas shop job.

Take the canvas off the boat if you can. It's much easier to work on a table.

If the button and socket are still riveted together but loose, cut or pry them apart with flat-nose pliers or end cutters. Work gently so you don't tear more fabric. Snip off loose threads around the hole.

A snap that won't stay closed but the fabric is fine: Sailrite explains that the socket has a small wire spring inside that grips the stud, and over years of opening and closing the spring loses its strength. The fix is a new socket, not a new stud. Sailrite's method is to drill off the old rivet from the rolled (socket) side with a drill bit slightly bigger than the rivet; it takes very little drilling before the button and socket come apart. Hold the button with pliers while you drill. Two things to check before ordering: whether it's a one-way Pull-the-DOT socket (it has a ramped inner edge and the name on the cap) or a normal one, and whether the old parts are nickel-plated brass or stainless. Sailrite says the easiest way to tell is to cut an old socket in half with tin snips (brass shows yellow inside) and warns not to mix brass and stainless parts. Standard marine snap caps are about 5/8 inch across.

Cut a patch of matching canvas. Boating Magazine recommends making it at least four times bigger than the hole; bigger is better. Round the corners so they don't peel. Attach it to the underside:

• Sew it around the edge with UV-resistant thread (PTFE thread outlasts standard polyester), or
• Glue it with an outdoor-rated fabric adhesive and weight or clamp it for several hours, as the label says.

Iron-on patches usually don't hold on marine acrylic.

Put the canvas on a cutting block or scrap of hardwood. Punch a 1/8-inch hole through the canvas and patch with a hole cutter and mallet, or a drill hole cutter. An awl works in a pinch. If the old spot is too damaged, punch the new hole close by and use a snap extender to bridge the gap to the existing stud.

1. Push the button through the hole from the outside so its post sticks out the underside.
2. Put the socket over the post on the underside.
3. Nest the button in the matching side of the anvil.
4. Line up the setting tool and give it a firm, sharp blow with the mallet (or squeeze a press or plier tool hard). You're riveting the button to the socket.

Boating Magazine found a hammer-set tool better than cheap pliers on thick, doubled seams. Press-type tools punch and set in one go and leave a hand free to hold the canvas. Test the snap: it should not spin loosely in the fabric.

If the boat-side screw stud is bent, corroded or loose, unscrew it and fit a new one in the same hole. Use the same screw type (stainless for marine use). Put a dab of marine sealant on the screw so water can't wick into the deck. A stripped hole into a cored deck or hull needs proper repair, not a bigger screw.

Adding studs for a new cover (a common question when a new cover arrives without matching snaps): BoatUS's method is to fit the cover on a calm day, line it up using its seams and corner patches, and add just one snap and stud as an anchor. Then work around the edge, pulling the canvas snug and marking each next spot with a grease pencil. Before drilling, check the screw size against the stud and drill a test hole in scrap, look behind the surface for wiring, tanks and hoses, and seal each hole as you set the stud. Practice setting a snap or two in scrap canvas first. Leave a little slack if your fabric shrinks in cold weather, or keep a few snap extenders handy.

Lift-the-Dot fasteners have a socket on the canvas held by small prongs bent over a backing plate, and a stud on the boat. They release only when lifted on one side.

• To remove: pry each prong straight, then lift off the plate and socket.
• Check the fabric. Reinforce it with a patch if it's torn (step 5).
• To install: push the new socket's prongs through the fabric, put the backing plate on, and bend each prong inward over the plate. Tap them flat with a soft mallet or a hammer and wood block. Don't hit hard enough to crush the socket.
• Line the socket up so it releases in the direction you want. The release side is usually away from the strain.

Twist fasteners use an eyelet in the canvas that slips over a turn button on the boat. Remove the old eyelet by bending its prongs back or cutting it out. Reinforce the fabric if needed, cut the slot to match the new eyelet, then fit it and bend its prongs over the backing plate. If the turn button on the boat is corroded or loose, replace it the same way as a snap stud (step 8).

If the teeth look fine but the zipper splits behind the slider, the slider is usually worn or spread.

1. Note the zipper size (often stamped on the back of the slider, such as #5, #8 or #10) and type: molded plastic teeth or coil. Buy a replacement slider that matches both.
2. At the open end, remove the stop with pliers, or open a few stitches of the end seam if there's no stop.
3. Slide the old slider off and feed the new one on the right way round, with both rows of teeth entering evenly.
4. Refit the stop or re-sew the end so the slider can't come off.

Missing or broken teeth, or a zipper that's chalky and brittle from sun, needs a new zipper. That's a sewing job a canvas shop can do quickly.

Rinse snaps and zippers with fresh water after salty trips. Lubricate them every few weeks with a snap and zipper lubricant or wax. Open and close every zipper and snap now and then, even ones you rarely use, so they don't seize. Log repairs in BoatMend so you can see which spots keep failing.