HOLD mechanical door holder, machined metal render
Mechanical door holder · Independent project

HOLD

Holds the door. Leaves no mark.

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A portable door holder with a spring-loaded snap-lock in a compact housing. It clamps onto the door, holds it open on plain friction, and comes off without leaving a trace.

ProjectIndependent project · Product development
RoleEverything. Concept, mechanism, CAD, prototyping and testing.
DurationThree weeks
StatusWorking prototype, 3D-printed and tested on a real door
The challenge

Hold a door still, without touching a screwdriver.

The whole problem is force without damage. HOLD had to clamp onto a door with no drilling and no permanent mounting, keep a consistent grip through repeated use and dynamic loads like wind, and stay planted on the floor. That meant the spring-loaded arm had to press down hard enough for friction to do the holding, while the snap-lock gave the arm fixed positions without piling on mechanical complexity.

3D-printed HOLD prototype clamped on a door, arm deployed against the floor
How it works

A snap-lock for position. A spring for grip.

The snap-lock sets the arm in a defined position. The spring-loaded arm transfers force downward into the floor, and friction does the rest. The housing geometry routes the load from the door through the structural body and the clamp interface, so the door itself never carries anything it was not built for.

Render of HOLD showing the spring and snap-lock arm
Side profile render of HOLD with the arm deployed
In motion

One hand. Snap down, lift off.

This is the 3D-printed prototype working on a real door. Snap the arm down and the door stays where you left it. Lift the arm and walk through.

Process

Three concepts went in. One came out.

I developed three mechanical concepts and scored them against each other before committing to a force logic. The winner combined the snap-lock with the spring arm. From there the complete assembly was modelled in CAD to check alignment, tolerance stacking and load paths, then refined over iterations to cut mechanical play without losing the compact proportions. The prototype was printed, clamped onto a door, and tested.

3D-printed HOLD prototype showing spring and arm
3D-printed HOLD prototype, side view of housing and arm
HOLD prototype clamped on a door edge with the arm locked up
The numbers
3weeks from first sketch to a working prototype on a door.
3mechanical concepts evaluated before committing to one force logic.
0holes in the door. The clamp mounts without tools and comes off clean.
What I took from it
  1. 01In a compact mechanism, tolerances are the design. Small geometric deviations show up as play immediately.
  2. 02Friction is a system, not a number. Spring force, floor material and wear all get a vote.
  3. 03A prototype on a real door answers questions a CAD model can only guess at.
Reflection

HOLD sharpened how I think about force in small mechanisms. Getting the snap-lock and the spring arm to share one load path took precise tolerance control — every deviation showed up as play or misalignment.

Friction-based holding is sensitive by nature. If I took HOLD to production, I would start with fatigue testing of the spring and refining the rotating interfaces, because long-term durability lives exactly there.