The Custom Swivel Phone Holster: Parametric Sizes

This project started because I had to find a way to stop carrying my phone in my pocket. I was starting to get Meralgia Paresthetica (often called "Phone Thigh Syndrome"), a condition where pressure on the lateral femoral cutaneous nerve causes numbness and pain in the thigh.

I couldn't find a commercial holster that fit my specific custom phone case, so I built my own. After multiple design iterations and weeks of field testing, I’ve developed a system that is strong, reliable, and easy to use. I can now snap my phone into the holster without looking. I use it daily and it has never fallen out.

High-Strength Design

To ensure this holster survived daily wear, I designed the frame in two parts: the Beam and the Cross Member. By printing these separately, I was able to orient the parts on the print bed to ensure the layer lines provide maximum structural integrity against the forces of a heavy phone. I used Black Carbon Fiber PETG for the best balance of rigidity and durability.

• 5mm Brim recommended as the parts should be printed standing on the long edge

• Print in default orientation

• Supports are optional. The Beam is the only part that might need them, but it is angled to make support unnecessary. Though they may be needed if you use larger layer heights.

The Clip System

The holster features a 360° swivel and a unique locking clip:

• Zigzag Jaws: Large "teeth" designed to bite into pockets or waistbands.

• Smooth Jaws: A single retaining tooth optimized for belts.

• Locking Slider: The Clip Retainer snaps up to open the jaws and down to lock them securely in place.

Measurement Guide

Because every phone case is different, you can download a custom STL with your exact dimensions. To get the perfect fit, measure your phone (or the phone in its case) using calipers:

1. Width: Measure the width. Don't add tolerance for a nice tight fit.

2. Height: Measure the total vertical length.

3. Depth: Measure the thickness of the phone or case.

4. Tolerance: You can add as much as 0.5mm to these measurements to keep it secure without being too tight to fit or too loose and rattle.

Parametric Sizing

download a custom STL with your exact dimensions

Assembly & Hardware

• Hardware Needed: (1) 10mm M5 screw and (1) M5 threaded heat insert.

1. The Frame: Glue the Beam and Cross Member together (align the center swivel hole).

2. The Clip: Press the heat insert into the Clip Jaws.

3. The Swivel: Pass the M5 screw through the Swivel, insert the Swivel into the Frame and screw into the Jaws.

4. The Retainer: Slide the Clip Retainer onto the Jaws until it snaps into its tracks.

Optional Improvements

I added this velvet backing to the inside of the holster to have a gentle surface for the phone to rest on. But be careful to leave a circle of the backing that covers the adhesive over the spot where the swivel part is, so that the holster can rotate unhindered. I highly recommend this because I believe that in one of my earlier versions, glue or friction damaged the screen protector that was on the phone.