Simple recursive function to build a list of paired points (line segments) that also loops back to first element.

get-lines.rkt

#lang racket

(define shapes '(((0 0) (0 110) (220 0 ) (220 110))
                 ((1 1) (1 111) (221 1 ) (221 111)))
  )

(define (get-lines shape output)
  ;; do we have enough elements to build a pair?
  (if (> (length shape) 1)
      ;; ... more than one element (build pair and recurse)
      (let* ([p          (list (take shape 2))]
             [rest       (list-tail shape 1)]
             [new-output (append output p)])
        (get-lines rest new-output))
      
      ;; ... just one element (take first from output and return)
      (let* ([last-el    (first (take shape 1))]
             [first-el   (first (first output))]
             [p          (list (list last-el first-el))]
             [new-output (append output p)])
        new-output)))

(map (λ (shape)
       (printf "~s~n" (get-lines shape '()))) 
     shapes)

;; Example output:
;; (((0 0) (0 110)) ((0 110) (220 0)) ((220 0) (220 110)) ((220 110) (0 0)))
;; (((1 1) (1 111)) ((1 111) (221 1)) ((221 1) (221 111)) ((221 111) (1 1)))