Traditionally, bridges gain their strength through the triangular arrangement of their beams. This principle applies equally to miniature bridges made of toothpicks. When you arrange the toothpicks into triangles and fit the triangles together, you are increasing the structural integrity of the bridge and its ability to bear heavier loads. The tighter the triangles are that compose a bridge, the stronger the bridge is. You can also achieve more strength by reinforcing the triangle frame with other triangles. For example, a four-sided pyramid, or tetrahedron, is much stronger than a simple triangle of toothpicks.

- Skill level:
- Moderate

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### Things you need

- White glue
- Newspaper

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## Instructions

- 1
Lay down a layer of newspapers over your work area to protect it from any messes.

- 2
Fit three toothpicks together in a triangle, gluing them together at the tips. Do not let the tips touch in a precise manner. Instead, offset them slightly so that one tip touches the other toothpick a little way down from its tip. The corners of your triangle will be much stronger if you do this, reducing the chance that they will break.

- 3
Set the triangle on its edge and glue three more toothpicks to it when the triangle's glue is dry. Each toothpick should touch one of the triangle's points. Glue the other ends of the new toothpicks together to form a tetrahedron.

- 4
Build 18 more toothpick tetrahedrons exactly as you made the first one.

- 5
Glue the tetrahedrons together in a truss that is 10 toothpicks long by alternating upright and inverted tetrahedrons.

- 6
Create 38 more tetrahedrons and glue them together to form two more trusses that are 10 toothpicks in length.

- 7
Lay two trusses next to each other. There should be a groove running down the middle between them. Turn the third truss onto an edge and insert it into the groove. Glue the trusses together in this arrangement.

- 8
Create 39 more tetrahedrons. From these, assemble three trusses that are each seven toothpicks long.

- 9
Arrange two of the trusses next to each other and glue them to the top of your bridge. Turn the remaining truss on its edge and insert it into the groove between the seven-toothpick-long trusses. Glue it in place.