a ground opener that is allowed to caster in one direction is associated with a pair of arms connected by a pivot connection that allows one arm to move relative to the other arm . the movable arm is forced against the stationary arm when the ground opener impacts the soil as the ground opener is pulled along a relatively straight travel path . when the ground opener is turned radially from the straight travel path , the movable arm may cast away from the stationary arm . the disc opener is coupled to the movable arm through a central hub and , as such , the trailing edge of the disc opener will move away from the stationary arm as the disc opener is turned . when the disc opener has completed the turn , the torque on the disc opener will lessen thereby allowing the movable arm to move back toward the stationary arm .