This image shows the unique dovetail plate used to attach the declination assembly to the RA axis.  It affords a very positive, one way fit.  The two axis are held in place by the two silver locking knobs located at the bottom of the declination assembly.  As you can see, most of the mount is machined from solid aluminum with certain areas hollowed out.  This reduces weight while still retaining rigidity and strength. The RA assembly weighs 25 pounds, and the DEC axis is 15 pounds.  The standard counterweight shaft weighs 10 pounds.