between the two scissor sections ball bearings 31 fill the raceway and thus generally prevent wear by preventing abutting surfaces from rubbing and providing a rolling relationship therebetween this is best illustrated in fig4 a highly preferred feature of this invention comprises the formation of grooves 21 and 29 such that each comprises two surfaces such as 41 and 43 which intersect the inner surface such as 23 at differing angles the utilization of differing angles causes the ball bearing to move in a spiraling manner whereby wear is evenly distributed and does not result in any flattening of surfaces upon the ball bearings additionally a ball bearing casing 51 is provided between rotable scissor section 27 and axle 3 shims 53 and 55 are illustrated for housing the bearing case within the inner surface 57 of rotable scissor section 27 the utilization of a disc spring 59 is preferred in order to maintain some resiliency between the scissor sections and to thus permit ball bearings 31 to act as thrust bearings between the two surfaces in order to give some guidance as to the specifics of the structure it is preferred that surface 21 intersect the extended intersurface 23 at an angle of 53 degrees while surface 43 intersects at an angle of about 40 degrees to maintain an eighth inch diameter ball bearing therein it has been found that.