C-Thru Hinged Parallel Rule

This clear plastic ruler has two aluminum hinges and small positioning knobs that may be tightened or loosened. The lower left and upper right corners of the blades are marked: 18". The hinges are marked: THE C-THRU RULER CO. (/) BLOOMFIELD, CONN. U.S.A. Six circular slices of cork on the bottom of the instrument protect the surface on which it is used.
Teacher Jennie Zachs established the C-Thru Ruler Company of Hartford, Conn., in 1939. Although the firm was acquired by Acme United Corporation in 2012, it continues to make drafting tools and drawing instruments, including an aluminum version of this instrument. For other C-Thru products, see 1984.1071.12 and 1988.0807.02.
References: Brian Dowling, "Acme United Acquires Bloomfield's C-Thru Ruler," Hartford Courant, June 11, 2012; "About Us," C-Thru Ruler Company, http://www.cthruruler.com/.
Currently not on view
Object Name
parallel rule
date made
mid 20th century
C-Thru Ruler Company
Physical Description
plastic (overall material)
metal (overall material)
overall: 1.5 cm x 45.7 cm x 6.5 cm; 19/32 in x 18 in x 2 9/16 in
place made
United States: Connecticut, Bloomfield
ID Number
catalog number
nonaccession number
Parallel Rules
Science & Mathematics
Drafting, Engineering
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 Karen M. Lee

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