Last updated: September 2026
Field Fit is how Slides Rite installs high-quality standard doors in non-standard flex room openings without major construction. Using custom transoms, sidelights, sliding configurations, and finish carpentry, we engineer a design and installation method that makes a standard door work in an opening it was never built for. Most residential projects follow this path. Typical cost range: $7,000–$12,000 installed.
Every flex room entryway is different. The width, the height, and sometimes the shape of the opening all vary from home to home, and very few of them match the dimensions that standard door manufacturers build to. Field Fit is our term for the approach we use when a standard door can be made to work in a non-standard opening through custom design and installation methods applied on site. This article explains what those methods are, when each one applies, and why sliding door systems handle non-standard openings more flexibly than hinged door systems in almost every case.
What is Field Fit and how is it different from Factory Fit?
Field Fit means we work with high-quality standard doors and engineer a custom design and installation approach that makes them work in your specific opening. Factory Fit means the door itself is custom-manufactured to your exact opening dimensions at the factory. The result in either case is a finished installation that looks like it was always supposed to be there. The difference is in what is custom — the door itself, or the design and installation method.
Field Fit is generally the more cost-effective path when the opening is close enough to a standard size that one of the methods below can bridge the gap cleanly. When the opening is too far outside standard dimensions for any field method to produce a result we’re satisfied with, Factory Fit is the right direction.
Why do sliding doors work better for Field Fit than hinged doors?
Sliding door systems are more compatible with the Field Fit approach because their panels overlap when closed, giving them natural dimensional flexibility that hinged doors don’t have. Standard slab widths run from 24 to 36 inches in two-inch increments, and any opening between 96 and 144 inches wide can be covered by a sliding system using standard slabs before custom fabrication becomes necessary.
A hinged door requires a precise rough opening. The frame has to be built to exact dimensions that match the door width and height, which means any deviation from standard sizing has to be resolved before the door can be hung. That leaves less room for the kind of dimensional flexibility that Field Fit relies on.
What do you do when an opening is too tall for a standard door?
When an opening height exceeds what a standard door covers, the gap above the door needs to be addressed. We handle this two ways depending on how much extra height exists.
Glass transom
A glass transom fills the gap above a door when the opening is too tall for a standard slab. The frame is built on site to the exact opening width and fitted with a raw glass pane — clear, satin etched, or diffused white laminated. When the gap above the door is large enough to accommodate a proportional glass panel, we build a custom transom frame in the field during installation and order the glass as a raw pane sized to fit. The transom frame is built to the exact width of the opening and integrates with the door casing around it. Most customers prefer a single uninterrupted pane with no internal divisions — referred to as a full lite or one lite transom — though we can add trim or muntins in any pattern since the frame is being built custom on site.
This is one of the more visually impactful Field Fit solutions. A well-proportioned transom above a set of French doors or a sliding system fills the opening completely and gives the finished installation an architectural quality that makes it look like a deliberate design feature rather than a workaround.
Craftsman style header casing
When the gap above the door is too small for a transom to look proportional, a larger craftsman style header casing covers framing that builds the opening height down to accept a standard door. The casing acts as both the finish trim and the visual solution — its larger profile fills the extra height at the header in a way that reads as intentional millwork detail rather than a patch. This method works well for openings where the excess height is modest enough that a transom would look undersized and out of proportion.
How do you close off an opening that is too wide for a standard door?
Oversized width is the most common Field Fit challenge, and sliding door systems handle it more naturally than any other configuration.
Center-meet sliding door system
For openings between 96 and 144 inches wide, a four-panel center-meet sliding system using standard slab widths covers the full opening without any custom door fabrication. Two panels meet from each side at the center, and two end panels sit at the jambs. This is one of the cleanest Field Fit solutions available — standard materials, standard hardware, and a finished result that works proportionally across the full range of widths this method covers.
Center-meet with custom built glass sidelights or fixed end panels
For openings wider than 144 inches, we extend the center-meet system by adding custom built glass sidelights or additional fixed panels at each end of the opening to fill the remaining width beyond what the four standard panels cover. The sidelights are built in the field using the same framing and glass approach as the transom method described above. The center-meet panels handle the operable portion of the opening and the fixed panels complete the visual composition on each side.
Double French door with field built sidelights
When a customer wants swinging doors in an opening that’s too wide for a standard French door set — which caps at 72 inches wide — we install a standard French door within the opening and fill the remaining width on one or both sides with field built glass sidelights. The sidelights are fixed panels that bring the total visual composition to the full opening width while keeping the operable door at a standard size. This approach requires more precise opening modification than a sliding system but is the right solution when the homeowner specifically wants the look and operation of hinged French doors.
What options exist when an opening is too narrow for a center-meet system?
When an opening is less than 96 inches wide and a hinged door isn’t workable due to limited swing clearance, sliding systems are still the practical solution but the configuration changes.
Two-panel bypass sliding door
A bypass door covers openings between 48 and 96 inches wide where swing clearance is limited and a center-meet wouldn’t have enough width to function practically. Two panels on parallel tracks slide past each other rather than meeting at the center. Because only one panel needs to travel across the opening at a time, a bypass system works in narrower openings and keeps both panels on their floor guides throughout operation.
Fixed sidelight with sliding panel
For narrower openings where a bypass system isn’t the right aesthetic fit, we install a fixed glass sidelight on one side of the opening and a single operable panel that slides past it — integrated into the opening frame rather than mounted to the surrounding wall. The sidelight fills a portion of the opening width and the sliding panel covers the remainder when closed. This gives the finished installation a more composed, intentional look than a barn door while keeping the operation simple and the footprint within the opening.
Can Field Fit handle an opening that is non-standard in both width and height?
Yes. When an opening is outside standard dimensions in both width and height simultaneously, we stack the appropriate field methods. A wide opening with extra height might use a center-meet sliding system for the width and a custom transom for the height above it. A narrow opening with extra height might use a bypass door with a craftsman header casing. The methods are designed to work together, and the design consultation is where we work through which combination applies to a specific opening and what it will look like when it’s finished.
When does Field Fit stop being the right approach?
Field Fit works when the opening is close enough to standard dimensions that the gap can be bridged with finish carpentry, custom glass, or a carefully selected sliding configuration. When the opening dimensions fall outside the range where any of those methods produce a result we’re confident in, Factory Fit — where the door is custom-manufactured to the exact opening specifications at the factory — is the right path. The design consultation is where that determination gets made, and we’ll always be direct about which approach is the better fit for a given opening rather than defaulting to whichever one is easier for us to execute.
