The Main Sliding Tracks/Channels:

• 1. • Purpose: These are the actual grooves or raised rails within the uPVC frame of a sliding window or door. The “runners” (rollers/wheels) of the sash sit and move along these tracks.

     • Types:

       • 2-Track, 3-Track, or even 4-Track Systems: Depending on the design, a sliding window/door frame can have multiple parallel tracks to accommodate two, three, or four sliding sashes, often with an additional track for a mosquito mesh.

       • Integrated vs. Inserted: In most modern uPVC systems, the runner edges are an integral part of the main uPVC profile extrusion. However, in some cases, or for repairs, you might find replaceable metal (often aluminum) or harder plastic inserts that fit into the uPVC channel to provide a smoother, more durable running surface.

     • Wear and Tear: Over time, especially with heavy use or if debris accumulates, these tracks can wear down, become scratched, or get damaged, leading to stiff or jerky operation of the sliding sash.

  2. “Run-Up Blocks” or “Riser Blocks”:

     • While not strictly “runner edges,” these are sometimes referred to as related to the “running” mechanism. As seen in search results, a “uPVC Run Up Riser Block” is a small, wedge-shaped block that guides the opening sash upwards as it closes into the outer frame.

     • Purpose: This helps to lift a slightly dropped or misaligned sash into its correct position, allowing the lock points to engage properly and smoothly, reducing strain on the locking hardware.