Liniar bifold door repair.
We regularly assess Liniar uPVC systems for stiff or failing rollers, misaligned panels, worn seals, and locking problems affecting everyday use.
Positioning
Liniar is a UK profile manufacturer best known here for its ModLok 70mm uPVC bifold system. ModLok combines a uPVC profile with an aluminium outer frame, a captive top guide and bottom-running sealed roller mechanisms, and is made by independent businesses.
Liniar ModLok aluminium exoskeleton, sealed rollers and shootbolts — what we see most on Liniar doorsets
ModLok is bottom-rolling: the threshold carries the panel weight while a captive top track guides the panels. If a panel grinds or feels heavy, we check the threshold channel and top guide separately; cleaning or lubricating the wrong location will not correct a displaced running assembly.
The rollers use sealed bearings and are intended to run without lubrication. Track debris is therefore a more useful first observation than adding oil to the roller itself. We check the guide surfaces, the packing and the frame level before deciding whether a roller set has failed.
Liniar's locking layout is unusually identifiable: the master door can use opposing hooks and locking bolts, while slave panels use anti-lift locking bolts engaging into stainless steel track. A lock that will not engage can reflect a panel-position problem or incorrect compression, not simply a damaged central case.
The ModLok magnets and operating sequence also matter. If the magnets are not fully engaged when the doors are open, the mechanism can be operated out of sequence. We record that history alongside signs of seal wear, track obstruction and frame movement.
How the assessment supports the right repair.
The assessment follows nine connected stages, from reviewing the doorset’s history and measuring its condition to checking operation, components and manufacturer tolerances. The findings give us a clear basis for an accurate quotation.
We start with the background and history of the doorset, then take extensive measurements for distortion and check the frame for square and twist. We test operation under load, check drainage paths, and inspect glazing, gaskets and packers. Where parts are involved, components and part numbers are verified against the manufacturer, and every measurement and observation is cross-checked against the manufacturer's recommended tolerances. After that cross-check, we provide an accurate quotation based on the assessment findings.
The full process is set out stage by stage on our How it works page.
Open the assessment processWhat we assess
- Fractured or damaged hinges
- Broken, worn, or disconnected rollers
- Dragging, dropped, or misaligned panels
- Panels catching the threshold or header
- Difficult closing or locking
- Faulty locks, cylinders, handles, keeps, tracks, guides, and seals
How the assessment supports lasting performance
Pro-Lock assesses the complete doorset and recommends repairs with the aim of returning it to operation as intended by the manufacturer. Understanding how the panels, running gear, seals, locks and frame work together helps reduce unnecessary strain on connected components, support reliable operation and minimise repeat repairs over the long term.
An experienced engineer assesses the complete bifold doorset, talks you through the findings on site, and provides a written report with a quotation for any recommended repairs.
The findings are followed by a comprehensive report and itemised quotation by email, with repairs arranged separately. No repair work is carried out during the assessment.
The £79 fee covers a professional bifold-door assessment of the complete doorset. £79 professional assessment, credited against any repair, or refunded if we cannot quote. 12 month warranty on completed repair work.
You do not need to identify your doorset first.
You do not need to identify your doorset before getting in touch. Many bifold doors are unbranded or contain a combination of components from different manufacturers. Identifying the system, cross-checking component and part availability, and sourcing suitable parts through our established European network of suppliers is our job. Pro-Lock regularly repairs bifold door systems that other repairers have classed as obsolete, where a suitable repair route can be identified.
Warranty
All work carried out is backed by our market-leading 12 month warranty, covering our workmanship and any parts supplied and fitted as part of the repair where applicable.