Beam compass

Claim 1

A DRAFTSMAN''S BEAM COMPASS, COMPRISING: A RIGID BEAM HAVING UPPER AND LOWER PARALLEL SURFACES AND CONNECTING SURFACES AT RIGHT ANGLES THERETO; PIVOT CENTER MEANS SECURED AT ONE END OF SAID BEAM FOR ANCHORING SAID BEAM FOR SWINGING ABOUT SAID PIVOT AS A CENTER; AND A SCRIBING INSTRUMENT HOLDER CARRIED BY SAID BEAM FOR POSITIONING A SCRIBING INSTRUMENT A FIXED DISTANCE FROM SAID PIVOT MEANS, SAID HOLDER BEING A UNITARY SPRING MEMBER, BEING GENERALLY V-SHAPED IN PLAN AND HAVING A BASE AND TWO BIFURCATED LEGS EXTENDING DIAGONALLY THEREFROM, EACH LEG CLOSELY STRADDLING SAID BEAM THEREBETWEEN, SAID HOLDER INCLUDING A PAIR OF ROLLERS JOURNALLED IN THE TERMINAL ENDS OF EACH LEG AND BEING ROTATABLY SUPPORTED THEREBY IN UPRIGHT FASHION AGAINST THE SIDE OF THE BEAM OPPOSITE SAID BASE, SAID ROLLERS BEING SPACED APART, ONE ON EACH SIDE OF THE CENTER OF SAID SCRIBING INSTRUMENT, SO THAT THE CENTER OF THE ROLLERS AND THE SCRIBING INSTRUMENT DESCRIBE A TRIANGLE IN PLAN, SAID BASE BEING SHAPED TO CONFORM TO SELECTED SURFACES ON SAID SCRIBING INSTRUMENTS OF DIFFERENT SHAPES AND DIRECTLY FORCE THE SCRIBING INSTRUMENT AGAINST AN UPRIGHT SURFACE ON SAID BEAM, SAID SPRING BEING SPRUNG FROM ITS AT REST CONFIGURATION WHEN SO HOLDING A SCRIBING INSTRUMENT WITH SAID ROLLERS ENGAGING THE OPPOSITE UPRIGHT SURFACE OF SAID BEAM WHEREBY SAID SPRING HOLDS SAID SCRIBING INSTRUMENT IN FRICTIONAL ENGAGEMENT WITH SAID BEAM TO LOCK SAID INSTRUMENT AGAINST UNDESIRED RELATIVE MOVEMENT.