A piece of string can be an impressive geometric construction tool. When held down at one end, a string can be used to create a circle. When tightly stretched, a string can act as a straightedge.
The constructions below are samples of constructions using string. The steps to perform these constructions are the same as those followed when using a compass and straightedge.
Before beginning the construction, secure a piece of string to your writing utensil. To secure one end of the string to the paper, use a pushpin (as shown on this page), or secure the end by holding it in place with your free hand. Practice before you begin to see the method that works the best for you.
Construct a bisector of a segment. 
Steps: Bisect
1) Secure pushpin at A. Set string length more than half of AB. Swing arc.
2) Move pushpin to B. With same length of string swing another arc.
3) Draw line through points where arcs intersect.
4) This line is the bisector of the segment. 

Construct an angle bisector. 
Steps: Bisect ∠BAC
1) Secure pushpin at A. Set string length. Swing arc.
2) Move pushpin to arc's intersection on one ray. Swing arc in interior.
3) Repeat from other ray with same length string.
4) Connect A to intersection in interior of angle. 

Construct a perpendicular from a point not on a line. 
Steps:
1) Secure pushpin at P. Set string length past line. Swing arc.
2) Move pushpin to arc's intersection on line. Swing arc below line.
3) Repeat from other intersection with line with same length string.
4) Connect intersection of arcs to P. 

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