A simple heat inserts jig, which I've made for my cheap soldering iron.

It consists of the following parts:

1. Base - 1 pc;

2. Rail - 1 pc;

3.  Slider (tool holder) - 1 pc, it has holes for M3 screws, but they were not needed with my soldering iron;

4. Cap - 1 pc;

5. Elastic band holder - 2 pcs, optional, but required if you use elastic bands;

6. Box (bottom) -1 pc, optional;

7. Box tray - 1 pc, optional, can be used for storing heat inserts and soldering iron adapters;

8. TPU feet for the bottom - 4 pcs, optional;

9. Elastic bands - 2 or 3 pcs, optional, needed only if you need the tool to get to initial position.

You can use the jig perfectly fine without the optional parts. Nevertheless I think it  will be more functional and good looking with all of them.

Important note: Using some kind of grease or oil on the rail is highly recommended. 

I'll be happy if you give me some feedback and show my your prints.