How to Install a Window Trim Ring for Awning or Half-Slider Windows | Installation Guide

Last updated: September 24, 2026

Overview

Install a window trim ring around awning or half-slider van windows in about 1 hour using self-tapping screws. Window trim rings provide a finished edge around wall-mounted bunk windows.

Before You Start

  • Vehicle: Shown on a Ram ProMaster; the same steps apply to Mercedes Sprinter and Ford Transit

  • Kit: Awning Window Trim Ring or Half-Slider Window Trim Ring (Sprinter, Transit, and ProMaster versions available - see Related Resources)

  • Mounting location: Rear bunk window opening

  • Estimated installation time: ~1 hour

Tools & Materials

  • Scrap wood or plywood strips

  • Self-tapping screws

  • Measuring tape

  • Marker or pencil

  • Jigsaw

  • Router table with a flush-trim bit (or a hand router and a template)

  • Driver for final fastening screws

Installation Instructions

  1. Temporarily mount the trim ring. Cut a few 4–6" spacer strips and self-tap them to the wall so you can hold the ring in place for measuring.

  2. Measure to the flange. Take measurements to the top, bottom, and sides of the trim ring's flange.

  3. Transfer to your panel. Mark those same points on the back of your wall panel, then trace the trim ring's inside and outside profile.

  4. Lay out your screw pattern. Mark mounting holes about 3/4" in from the outside edge, spaced for six total mounting points.

  5. Mark a rough-cut line. Draw a second line about 1/2" inside your final cut line — this is what you'll jigsaw to.

  6. Rough-cut the opening. Cut along the rough line with a jigsaw.

  7. Flush-trim to the final line. Finish the edge on a router table with a flush-trim bit. The pilot bearing can overheat and scorch the plastic on a long cut, so take a cooling break partway through.

  8. Fasten the trim ring to the panel. Install the finished ring and panel together as one unit.

Window Trim Ring Installation Video

Watch the install below; it's shown on a ProMaster, but the same process applies to Sprinter and Transit.

Related Resources