45 degrees with the horizontal or 45 degrees with the vertical.
Thomas E. French and Carl L. Svensen Mechanical Drawing For High Schools (New York: McGraw-Hill Book Company, Inc. , 1919) 7
2400×2008, 286.5 KiB
1024×856, 42.9 KiB
640×535, 22.9 KiB
320×267, 9.9 KiB