Rolling Parallel Rule and Combination Instrument

This 12" clear plastic rolling parallel rule is combined with a scale of inches that is divided to 1/16"; a centimeter scale divided to millimeters; and a protractor divided to 5° and numbered by 30s from 0 to 90 to 0. Holes in the scales at every 1/2-inch and centimeter help the user align the instrument on a drawing. The holes may also be used with a pencil to produce parallel lines. The instrument is marked with a small centimeter-inch conversion table and the words: MADE IN TAIWAN.
The white roller is also marked with various useful mathematical formulas, a small table of sines and cosines of various angles between 1° and 45°, and comparative centimeter and inch scales that function as a line spacing guide for measuring evenly spaced lines.
The rule appears to be model 1205 of Hua Ching Manufacturing Co., Ltd., which has been making plastic and wooden drafting supplies in Taichung, Taiwan, since 1978. Several firms currently distribute the rule in the United States for a price of about $10.25.
Reference: Hua Ching Manufacturing Co., Ltd., "About Us,"
Currently not on view
Object Name
parallel rule
date made
Physical Description
plastic (overall material)
overall: 2.5 cm x 31.3 cm x 6 cm; 31/32 in x 12 5/16 in x 2 3/8 in
Place Made
Taichung, Taiwan
ID Number
catalog number
accession number
Parallel Rules
Science & Mathematics
Rule, Measuring
Drawing Instruments
See more items in
Medicine and Science: Mathematics
Parallel Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Tony Brooks

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