Free images results:
 

Rule pictures, stock photos and images

 
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Sign Royalty Free Stock Photos
Author: Mbagdon
Sign Stock Photos
Author: Mbagdon
Agenda Royalty Free Stock Photography
Author: Studio
Dictation Royalty Free Stock Image
Author: Studio
Sign Royalty Free Stock Photography
Author: Mbagdon
Frame Stock Images
Author: Coleopter
 
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Also, here are some commercial RF-licensed images that match your search criteria:  
Rule lines Royalty Free Stock Photography
Author: Gmdsgn
Slide rule Royalty Free Stock Photos
Author: Coprid