MRU (Multiboard Rack Unit) is a Multiboard remix project by RetroDuck89 that lets users construct 3D-printed equipment racks using the Multiboard ecosystem.
MRU is designed to feel like a natural extension of Multiboard: introducing custom parts only where standard Multiboard pieces alone cannot solve the problem, while preserving on-grid construction and modularity wherever possible.
MRU is currently in an early soft-launch phase while core parts and documentation are being refined.
This project was inspired by Jeff Geerling’s Project Mini Rack, which explores building compact, 3D-printed racks for homelab and computing projects.
- 📘 Project documentation: https://mini-rack.jeffgeerling.com/
- 🎥 YouTube video: https://youtu.be/y1GCIwLm3is
MRU builds on these ideas by integrating directly with the Multiboard system.
If you’re new to Multiboard, Jonathan from Keep Making provides an excellent overview of the ecosystem here:
- 🎥 Multiboard Primer Video: https://youtu.be/vXsgPpDz4ys
The term MRU is used in a few related ways throughout this project:
- The MRU Project — the overall Multiboard-based rack system
- MRU Rail Parts — the custom hybrid rails used to mount equipment
- MRU as a Unit — where 1 MRU = 50 mm of vertical height
MRU units align cleanly with Multiboard’s grid system:
- Multiboard 1 MU = 25 mm
- 2 MU = 1 MRU
For example, a 10 MU Multiboard L-beam pairs naturally with a 5 MRU rail.
- Enable users to build rack-mounted computing and equipment enclosures using the Multiboard ecosystem
- Introduce custom remix parts only when necessary, such as MRU rails and a small set of supporting accessories
- Offer compatibility with standard rack-mounted gear while retaining Multiboard’s modular, on-grid design philosophy
All MRU rails are hybrid by default unless otherwise stated.
The first released rail variant is the MRU T-Series rail, named for its cross-sectional shape.
Key characteristics:
- Hybrid front face offering standard rack spacing
- On-grid Multiboard threading for native accessories
- Lengths defined in 50 mm MRU increments
- Designed to nest into the inside corner of Multiboard L-beams
- Supports mirror-stacking to scale rack height across multiple segments
Additional rail variants or series may be introduced in the future and will be named by geometry.
For full design details, see: 👉 MRU-SPEC.md
If this is your first time working with MRU, start here:
The Getting Started guide covers:
- recommended first steps
- minimum parts to print
- suggested starter configurations
- hardware requirements
- how to avoid common early pitfalls
MRU rail installation can be somewhat finicky, especially during first assembly. Careful alignment and a staged approach are strongly recommended.
Before printing or assembling a full chassis, review:
- 🔧 INSTALLATION.md — rail mounting guidance and best practices
- 🛠️ TROUBLESHOOTING.md — common issues and how to resolve them
All currently released MRU parts are listed here:
The Downloads page includes:
- available MRU T-Series rail pairs
- file naming conventions
- slicing and printing notes
- versioning and beta status information
- links to live Thangs listings
MRU is currently in early public beta.
- Parts may evolve as feedback is collected
- Minor tolerance or threading adjustments are expected
- Documentation will continue to improve alongside hardware revisions
Feedback, testing results, and iteration reports are welcome and encouraged.
MRU is a community remix project built on the Multiboard ecosystem and is licensed under the Multiboard License.
Please review:
If you remix or extend MRU parts, please follow the same license terms and provide appropriate attribution.
A full introduction video and additional documentation are coming soon. For updates, follow along on YouTube: