While Don means "be parallel," DonHa' does not mean "be perpendicular." It means something like "be misaligned." The word for "be perpendicular" is leD and it's normally used with a plural subject: leD rav tlhoy je "the floor and the wall are perpendicular (to each other)." The word leD is also used to indicate a right angle: tajvaj leD. (through De'vID, 11/16/2014)