;Place sewer invert line (profile) from station to station.
(DEFUN C:invd ( / )
(while
  (setq prpb (car (entsel "\nSelect Beginning Station Line ")))
  (setq prpi (car (entsel "\nSelect Proposed Pipe Invert Line ")))
  (setq prpe (car (entsel "\nSelect Ending Station Line ")))
    (setq ptb1 (reverse (cdr (reverse (cdr (assoc 10 (entget prpb)))))))
    (setq ptb2 (reverse (cdr (reverse (cdr (assoc 11 (entget prpb)))))))
    (setq pti1 (reverse (cdr (reverse (cdr (assoc 10 (entget prpi)))))))
    (setq pti2 (reverse (cdr (reverse (cdr (assoc 11 (entget prpi)))))))
    (setq pte1 (reverse (cdr (reverse (cdr (assoc 10 (entget prpe)))))))
    (setq pte2 (reverse (cdr (reverse (cdr (assoc 11 (entget prpe)))))))
    (setq pt1 (inters ptb1 ptb2 pti1 pti2 nil))
    (setq pt2 (inters pte1 pte2 pti1 pti2 nil))
  (command ".line" pt1 pt2 "")
);while
(PRINC)
);defun