to its open end preferably interior surface 452 also includes a beveled lead in region 468 adjacent guide surface 466 at the open end of slot 426 pinion gear 416 includes at least one and preferably a pair of teeth 470 designed to engage teeth 462 of rack gear region 460 as first object 402 and pinion gear 416 are moved into engagement with pinion gear reception portion 420 and second object 404 see fig3 teeth 470 are positioned for engagement with teeth 462 of rack gear 460 then as handle 428 is pivoted to the retain position see fig5 teeth 470 of pinion gear 416 drive first object 402 in a linear fashion along linear rack gear region 460 until pinion gear 416 and handle 428 are in the retain position at this position the engagement of teeth 470 and teeth 462 prevent any linear motion of pinion gear 416 or first object 402 relative to second object 404 along rack gear region 460 i e along the x axis as illustrated in fig7 additionally pinion gear 416 includes a distal region 472 that abuts against distal surface 464 of reception portion 420 when pinion gear 416 is in the retain position this abutting engagement further prevents any movement in the x direction pinion gear 416 also includes a stop surface 474 disposed generally opposite teeth 470 for abutting engagement with guide surface 466 of reception portion 420 when pinion gear.