The running rail may sit within a larger threshold assembly. This service does not alter structural openings, waterproofing or the building envelope. Explain any water-entry concern separately rather than treating a track repair as a diagnosis or remedy for it.
Loose or damaged fixings can affect the running surface. Accessible fixing points need sound support for ordinary work to proceed. Deterioration beneath the rail may require a different assessment; covering it with a new section does not restore an unsound base.
Some systems accept a repair insert, while others do not. The insert must suit the profile, roller contact and available clearance. An improvised cover can change the panel height or movement, so compatibility should be established before materials are purchased.
Repair an accepted accessible rail or fit a compatible running insert or replacement section without changing the building envelope. Scope limits: Accessible non-structural running rails only. No threshold waterproofing alterations, drainage-system redesign, structural changes, major glazing or powered operators.