PerfectFit sash lock shims, cut to match our Solid Brass Sash Lock
PerfectFit sash lock shims make a window lock again without replacing anything. Most windows that won’t lock aren’t worn out — they’re out of alignment by a hair, sometimes just 1/16 of an inch, from decades of settling, paint layers, and wood movement. That tiny shift is all it takes to make the lock miss its keeper.
A shim under the lock or catch raises the hardware just enough to bring it back into line, so the lock catches again and pulls the meeting rails tight — closing the gap at the leakiest part of a double-hung window. These shims do exactly that, with one difference: they’re cut to the same outline as the base of our Solid Brass Sash Lock, not a generic rectangle. Set one under the sweep or the catch and it tucks in behind the hardware with the two screw holes already lined up. No measuring, no trimming, no re-drilling — and nothing sticking out past the edge of the lock.
If you’re already installing our brass locks, this is the shim that belongs in the box with them.
The details
- Made to fit: our Solid Brass Sash Lock — shaped to its base outline and screw pattern
- Shape: contoured to the lock base, so it hides underneath and looks like part of the hardware, not a spacer wedged under it
- Thicknesses: 1/16″ for minor misalignment, 1/8″ for larger gaps
- Stackable: combine thicknesses for 3/16″, 1/4″, or more
- Mounting: two countersunk screw holes matched to the lock, so flat-head screws sit flush — no re-drilling
- Material: white plastic that won’t absorb moisture, crack, or show through paint
- Sold in: 5 packs and 20 packs
How many you need
One shim per lock or catch does most single-window fixes. Keep the 5 pack on hand for a house full of windows, and the 20 pack for a full brass-lock install. If you’re not sure how far the rail has drifted, start thin — it’s easier to add a layer than to remove one after the screws are set.
Which thickness
Close both sashes and look at where the lock meets the catch. If the step is barely there, start with 1/16″. If there’s an obvious gap between the rails, go to 1/8″. Test-fit with the screws loose before you commit.
Made to pair with
These PerfectFit sash lock shims are cut for our Solid Brass Sash Lock — solid brass, unlacquered, sweep and catch with four screws. Buy the lock and the PerfectFit shims together and everything drops in aligned. Running a different lock? Our Universal Sash Lock Shims fit most traditional two-piece sash locks and are sold individually.
Where they work
Any wood double-hung window running our Solid Brass Sash Lock, from 1850s Greek Revival to 1940s Colonial Revival. One note: shims fix alignment, not binding. If the sash is sticking from paint buildup, swollen wood, or a failed balance, fix that first.
Frequently asked questions
What makes PerfectFit different from your Universal shims?
PerfectFit shims are cut to the same outline as the base of our Solid Brass Sash Lock, so they tuck in behind the hardware, the two screw holes line up, and nothing sticks out past the edge of the lock. Universal shims are a generic rectangle that fits most traditional two-piece locks and are sold individually.
What lock do PerfectFit sash lock shims fit?
Our Solid Brass Sash Lock. They’re sized to its base and screw pattern, so the shim tucks in behind the lock and the screw holes line up with no trimming.
What thicknesses do they come in?
1/16 inch for minor misalignment and 1/8 inch for larger gaps. They stack, so you can build up to 3/16 inch, 1/4 inch, or more.
Which thickness should I use?
Close both sashes and look at where the lock meets the catch. If the step is barely there, start with 1/16 inch. If there’s an obvious gap between the rails, go to 1/8 inch. Test-fit with the screws loose first.
How many come in a pack?
Two options: a 5 pack for single fixes and touch-ups, and a 20 pack for a full house or a whole brass-lock install.
What are they made of?
White plastic that won’t absorb moisture, crack, or show through paint, cut to the shape of the lock base with two countersunk screw holes.