Gantries may be cantilevered .
One sided on the left , right and center ( sometimes referred to as a half - gantry or Butterfly gantry ) , or they may be bridges with poles on each side .
Gantries may be cantilevered or one sided on the left , right and center ( sometimes referred to as a half - gantry or Butterfly gantry ) , or they may be bridges with poles on each side .