Triangular prism box maker
Triangular prism box template
Three long panels folded into a triangle, closed at each end by a triangle that tucks in. Set the side and the length; the ends follow.
How to fold it
Print at 100% on cardstock. A long bar box often fits a Letter or A4 sheet better turned sideways; the tool turns it for you.
Cut the outline, including the two end triangles with their rounded tuck flaps and the two small dust flaps.
Crease the two long lines between the panels hard: each one folds well past a right angle, to 120°, so the panels lean in to meet.
Fold the three panels into a triangular tube and glue the grey tab inside the floor panel, keeping the corners sharp.
Close one end: fold the dust flap in, lay the triangle over it and slide its tuck flap inside the slanted panel.
Slide the bar or the gift in from the open end and close it the same way.
How the template is drawn
Three panels at 60°
Each long crease turns 120°, so the three panels meet at 60° and the end is an equilateral triangle. The side you type is the inside side; each panel is drawn 0.4 mm (0.02 in) wider on cardstock, because a 60° corner pushes the walls out by 1.732 board thicknesses (the square root of 3).
End triangles
Each end is a triangle as wide as a panel and 38.9 mm (1.53 in) tall at 1.75 × 6 in: 0.866 times the side. It hinges on the floor panel, so the box lies on its floor with the ridge up.
Tuck flap
22.4 mm (0.88 in) deep: half the side, kept between 8 and 30 mm and never more than half the length. It is 0.8 mm (0.03 in) narrower than its edge at each end, so it slides inside the slanted panel without catching on the corners.
One dust flap an end
The panel on the far side carries a dust flap 11.7 mm (0.46 in) deep, 30% of the triangle's height. Its sides lean in by more than the 60° corners need, so it lies wholly under the triangle.
Room inside
The cross-section is 0.433 times the side squared: about 130 ml at the starting size, 43% of a square box with the same side and length.
Glue tab
12 mm (0.47 in) wide, at most 60% of a panel, glued to the floor panel's inside so its edge never shows on the slanted faces.
Bars, pencils and party favors
A prism box suits long, narrow things that stand up badly in a square box: a chocolate or soap bar, pencils and pens, a candle, a rolled note. Make it short and nearly as long as its side for a small favor box that stacks ridge to floor.
For a flat-sided bar box, the tuck end box uses the same tuck ends on four walls. A pyramid has triangular faces too, meeting at a point, and a pillow box or a gable box makes a softer favor. Square gifts go in a cube.
