show notching marks 320 on the flanges 310 of the rule 300 notching marks 320 are of different angles which can range from 0 degree to 180 degrees a notching angle of 0 degree would be no notching mark while a notching angle near 180 degrees e g between 140 and 180 degrees would be a flat notching mark fig4 shows one example of a sharp notching angle 400 as shown in fig4 in areas near the sharp notching angle 400 the flanges interfere with each other and the flanges must be filed and grounded to bend them into the sharp angle fig5 a shows a notching device 500 in accordance with one embodiment typically the notching device 500 is one of the units of a bending apparatus fig5 b is a top perspective view of the notching device 500 in accordance with one embodiment the illustrated embodiment of fig5 b includes four notching punches 510 512 514 516 of different angles e g 30 60 120 and flat or 180 degrees in one embodiment the notching punch 510 makes a 30 u00b0 notching mark in another embodiment the notching punch 512 makes a 60 u00b0 notching mark in another embodiment the notching punch 514 makes a 120 u00b0 notching mark in yet another embodiment the notching punch 516 makes a 180 u00b0 or flat notching mark in other embodiments notching marks of different angles can be made fig6 a shows the notching marks 600 610 612 614 616 618.