Make a Cardboard Corner Squaring Jig

WHAT TO GATHER

Your starting kit.

Clean, dry cardboard with uncrushed edges
A ruler, pencil, and scissors suitable for the board
Paper glue or paper tape as required by the joins
Scrap cardboard and a protective work mat

STEP 01

Measure and prepare

Cut two rigid cardboard strips about 40 by 200 mm and a square base 180 mm across.

STEP 02

Lay out the construction

Use an actual square or a verified paper right angle to align the strips at 90 degrees on the base.

STEP 03

Join and shape

Glue the strips in place and let them dry under a light flat board, then use the inner corner to align paper layers.

STEP 04

Check the result

Check the finished angle against your reference before relying on the jig for repeated layouts. Let all adhesive dry before fitting the intended lightweight contents. Place the project on a flat surface and check that its joints sit square. If a slot tears or a wall leans, remake that piece from sound cardboard rather than hiding the weak join with decoration.

STEP 05

Finish and keep

Smooth exposed rough edges with a thin paper covering where needed, without blocking working slots. Keep the project away from water and heat. Recheck the joints after a few uses and replace a worn piece if it bends or loses its shape.

Before you begin.

How wide should I cut the slots?

Measure the cardboard thickness and test a slot on an offcut. The pieces should slide together with light pressure; forcing them can crush the corrugation and weaken the join.

What should I check before beginning?

Check the finished angle against your reference before relying on the jig for repeated layouts.

Original editorial project guidance. Images are AI-generated concepts, not photographs of tested finished projects. Practice on inexpensive materials and follow tool and material instructions. Sources & approach.

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