Senior Landscape Architect Timothy J. Harlow shares his method for hatching at angles to match particular objects in a drawing.
"When you are hatching an area that has a different orientation, such as shingle-hatching sections of an octagon roof, use the user coordinate system, then Object to align each section. Type UCS on the command line, then type OB. Pick the object you want to match the rotation of, and you're ready."
Notes from Cadalyst Tip Patrol: Rotating the UCS (user coordinate system) will change the angle at which you will be drawing. If you don't want to mess with the UCS, then determine what angle the area is at and create your hatch at that angle. Rotating the UCS may be faster, however. To reset the UCS, type UCS on the command line, then W for world.