To drop a perpendicular to a chain line from a point out faid it
Select any point E on the line with C as center and CE as various show and arg to out the chain line if F by sect CD will be perpendicular to AB
Select any point D on the chain line. Join DC and by select it at E . with E as center and DE or EC as readies draw and arg to cut the chain line in F. FC will be perpendicular.
Select any point E on the chain line witch a center and as radius draw and arg to cut the chain line in F measure FD and FE obtain the point C by macking FC=〖FD〗^2/2FE joint C and D. CD will be perpendicular the chain line.