An open-source clamshell holder generator for openGrid, using the openConnect system. The holder can be used to mount objects either under a desk, often in combination with the Underware system, or on a wall. A common use case is holding power strips, but the dimensions and openings can be adjusted for a wide range of object shapes.

Several example .stl files are included, with the parameters used to generate them in the file names.

Customization guide:

1. Measure the item. Set "item_width", "item_height", and "item_depth". Adjust "item_corner_rounding" based on the item's shape. Add a little clearance if you want the item to slide in easily. For a heavy item, you may want to increase "holder_thickness" to make the holder sturdier.
2. Set "holder_slot_position". "Back" makes the item face forward when mounted on a wall, or downward when mounted under a desk. You can also choose "Top", which makes the item face sideways when mounted under a desk.
3. Adjust the front opening. Use "front_opening_left_right_margin" and "front_opening_top_bottom_margin". Larger margins create a smaller front opening, which may interfere with use, such as blocking the outlets of a power strip.
4. Adjust the side cutout(s). Use the "side_cutout_x_margin" parameters. The side cutout can be enabled on one side, both sides, or disabled completely. The position and size of the opening are customizable. Note the "side_cutout_top_margin" and "side_cutout_bottom_margin" starts where the "front_opening_top_bottom_margin" ends. It is designed so the cutout would only remove the front-opening edges when margins are set to negative values.
5. Set "holder_slot_column_limit". This value defaults to the minimum of 1, which saves filament and helps with heat dissipation. Increase it if you want the holder to cover more of the item.
6. Set "slot_slide_direction". "Left" and "Right" are usually used for under-desk mounting, while "Up" and "Down" are usually used for wall mounting. Choose the direction that lets the holder slide onto the openConnect slots from the accessible side.

"generate_holder_part": "Both" shows a good preview of the result, so it is recommended during customization. The "Left" and "Right" options allow different parameters for each part and automatically orient the model for 3D printing, which is convenient when exporting the result.

The model is open-source under the CC-BY-SA license. Like all the OpenSCAD models I've designed for openGrid, it can be found in this GitHub repository. Feel free to use the code; feedback and suggestions are welcome.

2026-07-23 Update: Made the default calculation of slot count more generous. Added “skip_slot_fit_check” and manual slot count adjustment options.

2026-07-15 Update: Changed the orientation of the model for better preview. Renamed some parameters and added comments.