If you’re restoring old wood windows, there’s a point in the job where the sash is out of the frame and on the bench. Maybe a sash cord broke and you’re rehanging it. Maybe you’re replacing cracked glass or reglazing. Either way, the stiles are bare and easy to work on.
That’s the best time to add sash spring bolts.
What is a sash spring bolt?
A sash spring bolt is a small spring-loaded pin that mounts through the side stile of a window sash. The stile is the vertical piece of the frame on each side of the glass. On the inside there’s a pull knob. On the outside edge, the bolt seats into a hole drilled in the window jamb, which is the fixed frame the sash slides in.
Pull the knob and the bolt retracts. Move the sash. Let go, and the spring pushes the bolt into the next hole it lines up with.
They go in pairs, one on each side of the sash. A single bolt holds one side and lets the sash rack, or twist, in the frame.
You’ll also see them called window spring bolts, sash bolts, sash locks, or window stop pins. They’re a common hardware form on older wood windows.
How spring bolts work with sash cords
A properly restored double-hung window is counterbalanced. Cords or chains run over pulleys to cast iron sash weights in the wall, and the weights offset the sash so it moves easily and stays where you leave it.
Spring bolts add the next step: they lock the sash in place. The weights make the sash easy to raise and lower. The bolts hold it at the height you choose, open or closed.
When should you install sash spring bolts?
While the sash is out of the frame for cord replacement, reglazing, glass replacement, or paint stripping.
The stile is accessible. With the sash on the bench, you can drill the stile straight and square instead of working at an angle in the frame.
You’re already finishing. If you’re stripping, priming, or painting the sash, the bolt holes get done in the same round of work.
You can plan the stops. With the sash back in the frame, raise it to the heights you want, mark the jamb, and drill the receiving holes before the stops and trim are closed up.
It’s one trip. Pulling a restored sash back out later means removing stops and parting bead again.
What do sash spring bolts do?
Lock the window open for ventilation. This is why most people add them. Set a receiving hole a few inches above the sill and the window can stay cracked for air. With the bolts seated, the sash can’t be pushed up from outside. That matters on ground floors and in bedrooms.
Lock the window closed. A hole at the closed position turns the bolts into a window lock. The sash stays down until someone pulls both knobs from inside.
Set fixed open positions. Two inches, six inches, halfway. Drill where you want the window to stop and it stops there every time.
What windows do sash spring bolts fit?
Wood windows. That includes single-hung and double-hung sash, storm windows, removable and stationary screens, hinged screens, and outswing casements, mounted inside or outside.
The turned ball knob suits Victorian, Edwardian, Colonial Revival, Craftsman, and Arts and Crafts houses. Match the finish to the rest of your window hardware, such as sash locks and lifts.
The unlacquered brass has no clear coat, so it darkens with handling and air. The nickel and bronze finishes are applied over the brass body.
Window Spring Bolt Installation Instructions
Solid Brass | 3-1/4″ Overall Length
Product Information
This solid brass spring bolt is designed to hold traditional wooden sash windows in a partially open position. It may be installed on either the upper or lower sash of a double-hung window, provided the window construction allows proper installation and operation.
Tools Required
Electric drill
3/8″ drill bit
5/16″ drill bit
Measuring tape or ruler
Pencil or marking tool
Wood clamp or suitable support
Installation Instructions
Step 1 – Remove the Window Sash
Carefully remove the sash from the window frame. Removing the sash allows you to drill straight through the side stile without interference from the window glass or surrounding frame.
Step 2 – Determine Bolt Placement
Select a location on the sash's vertical side stile.
Position the pull knob toward the interior of the room.
The spring-loaded plunger must face the window jamb.
Verify that sufficient solid wood is available to accommodate the bolt housing without contacting the glass or glazing.
Step 3 – Drill the Mounting Hole
Drill a straight 3/8″ diameter hole through the wooden sash stile, aligned with the intended bolt position.
Keep the drill perpendicular to the mounting surface and avoid damaging the surrounding wood or glass.
Step 4 – Install the Spring Bolt
Carefully insert the brass housing into the drilled hole, positioning the spring-loaded plunger toward the window jamb.
The pull knob must remain accessible from inside the room.
Press the housing into place without striking or damaging the knob or spring mechanism.
Step 5 – Mark the Receiving Hole
Temporarily reinstall the sash and position it at the desired open height.
Mark the location where the spring-loaded plunger contacts the window jamb.
Step 6 – Drill the Receiving Hole
Drill a receiving hole approximately 5/16″ in diameter at the marked location.
The hole should be deep enough to accommodate the extended plunger without binding.
Additional receiving holes may be drilled at different heights to allow multiple window-opening positions.
Step 7 – Test Operation
Reinstall the sash and test the spring bolt.
Pull the knob to retract the plunger, move the sash to the desired position, and release the knob to engage the receiving hole.
Verify that the bolt operates smoothly and securely engages the jamb.
Upper Sash Installation
This spring bolt may also be installed on the upper sash of a traditional double-hung wooden window.
The installation procedure is generally the same as for the lower sash, with several additional considerations:
The upper sash typically operates in a separate track behind the lower sash.
The bolt must be positioned so the pull knob remains accessible from inside the room.
The plunger must align with a suitable receiving surface on the jamb.
Confirm that the bolt does not interfere with the lower sash, parting bead, window stops, or other hardware.
Verify that the upper sash has sufficient solid wood for drilling and installation.
Important: Not all double-hung windows have sufficient clearance for upper-sash installation. Check the window's construction before drilling.
Important Installation Notes
Designed for traditional wooden sash windows.
Remove the sash before drilling whenever practical.
Verify all measurements and clearances before drilling.
Do not drill into glass, glazing, or structural window components.
The bolt is intended to hold a sash at selected ventilation positions. It is not a substitute for a window lock, fall-prevention device, or sash support mechanism.
The installation dimensions above are based on the bolt's specifications and comparable spring-bolt installation methods, rather than a model-specific manufacturer instruction sheet.
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The Heritage Standard
Restored by hand, one at a time. Old wire out. New wire rated for present use, sound sockets, and grounding where the fixture allows. The body, glass, finish, and the marks it earned stay. Every fixture is tested on the bench before it leaves the shop.
About the Founder
Joe Golda has run Vintporium from his workshop in San José since 2008. He sources the pieces, pulls the old wiring, rewires them, finishes them by hand, and packs them himself. One person, one bench, one standard. Every fixture is tested — each socket, each switch — before it ships. What's original is called original. What's new is called new. We call this commitment to candor and craft our Heritage Standard.
1-408-387-0845
joe@vintporium.com
