a base comprising a body comprising a step formed in an upper surface having a hinge portion, a socket and a recess, and a track portion formed on a lower surface adapted to engage the track with movement there-along, said base having a rod opening located on a side thereof extending through said base to said step, said hinge portion comprising a first knuckle formed at one end of said step, said first knuckle having an opening dimensioned to receive a pin extending through said first knuckle and extending at least partially through said base, and said socket configured to receive a ball joint;

an arm comprising a first arm side having an arm hinge portion, a socket portion, and a protrusion, said arm hinge portion having a second knuckle formed at an end of said first arm side having an opening dimensioned to receive said pin to operably connect to said hinge portion of said base, said protrusion dimensioned to be received in said recess of said base when said arm is in a closed position, said arm further comprising a second arm side having a sleeve head receiver with at least one mirrored rotational inhibitor and a cross nut opening aligned with said rod opening when said arm is in a closed position;

an adjustable cross nut assembly, configured to be received in said cross nut opening, comprising a sleeve body having a first sleeve end with a sleeve opening having a thread engagement portion with at least one internal thread start, said adjustable cross nut assembly further comprising a sleeve head disposed at a second sleeve end of said sleeve body, said sleeve head having a plurality of rotational inhibitors;

a clamp assembly comprising a rod with a first end operably connected to a handle and with a second end having a threaded portion with an external thread start, said rod configured to be received by said rod opening and said second end configured to be received in said thread engagement portion of said adjustable cross nut assembly;

wherein said adjustable cross nut assembly is rotatably adjustable in said sleeve head receiver of said arm such that said at least one mirrored rotational inhibitor is configured to be received by at least one of said plurality of rotational inhibitors of said sleeve head when said arm is in a closed position such that said at least one internal thread start of said sleeve body maintains a first thread start position; and

wherein tightening of said handle of said carriage assembly achieves a simultaneous clamping effect of both said track and said extremity holder.