  Your bridge must be free-standing, and span a gap of 30 cm. It will sit on a piece of plywood that has a hole in the centre; this is to attach the strap which will hold the weights used to test the bridge.  The bridge roadway should be at least 5 cm wide and 30 cm long, and be able to accommodate the testing strap. The roadway need not be filled in ... a row of toothpicks on either side is acceptable. But it must be level. There must be a space under the bridge of at least 5 cm, and not more than 10 cm, that runs the length of the span. White glue may be applied only to points of contact; toothpicks may not be soaked or coated with glue. When your bridge is tested, it will 'fail' when the roadway breaks, or flexes more than 2 cm. Your bridge will receive an 'efficiency' rating, calculated as follows: Clearly, the more mass your bridge will hold, the better, ... but the more your bridge weighs, the lower its score will be. Don't use too many toothpicks! This contest can be won with no more than 35 g of toothpicks.  Here's an example of some wonderful toothpick bridges that illustrate the possibilities when designing with toothpicks. Anything is possible! The photo was sent to us by a visitor to our site, Charles from the University of Toronto. Bridge Structures | Bridge Photos | Using Toothpicks | Marshmallows | Make a Plan |