Challenge HLO: test-tube rack

Last updated: 30 October 2026

The tubes have a diameter of 16 mm.

Want to see every step with screenshots? Follow the build guide for the test-tube rack.

Steps

1. Drag a Box onto the workplane. Make it 100 mm long, 30 mm wide and 20 mm high.
2. Drag a Cylinder and choose Hole. Set the diameter to 17 × 17 and the height to 20 mm.
3. Raise the cylinder so it starts 5 mm above the base of the box. Its top then sticks out 5 mm. This makes a hole 15 mm deep and leaves a 5 mm floor.
4. Put the first cylinder in the middle of the width, 17 mm from the left end. Copy and paste it three times. The centres are at 39, 61 and 83 mm from the left end (22 mm spacing). Use Align so all four cylinders are centred in the width.
5. Select everything and click Group. Now the holes are cut.
6. Add a Text shape with your name. Choose a bold font and set the height to 1 mm. Put the text on the front or the top.
7. Check: a 16 mm tube in a 17 mm hole has 0.5 mm clearance on each side. The walls between the holes are 5 mm thick.

Success

All 4 tubes fit with a little room. The rack stands stable.

Stretch ideas

A drip tray, a slot for a label, or a wider base so the rack stands more steadily.