The secondary mirror is carried by a four-legged structure called the quadrapod, or top end. It is transported to the observatory on a special base, actually the alignment fixture for welding it together, and put onto the telescope with a special crane with two lines attaching to two of the legs just below the attachment points for the cross braces.

The top end must be placed in the telescope, tensioned, have its centering checked (at least initially), then shimmed, and retensioned. Next, the secondary mirror goes in.

1. The quadrapod is aligned with a plumb bob hanging from the center of either an alignment fixture or the secondary mirror, as explained under the procedure for aligning the telescope.
2. Once the quadrapod is attached to the tube (mirror cell) the guy wires must be tightened with the turnbuclkles. This is a two-step process. Set up the tensioning gauge on the four cables in succession. In the first step, tension each cable to a reading of 10 (using a 5/32 Allen wrench, or equivalent rod, through the hole in the body of the turnbuckle, holding the upper screw fixed with an adjustable wrench); next, tension them all to 18, corresponding to about 500 pounds of tension. Tip the telescope to a large zenith distance, and use the gauge to make sure the lowest cable is still in tension. After final tensioning, recheck the centering of the top end, if possible.
3. The next step is putting the secondary mirror in. The mirror and its cell weigh about 40 pounds and should be lifted into place with a special lifting fixture. Attach it to the two aluminum standoffs on the mirror cell with 1/4-20x1 screws. Hook the crane to the eye bolt in the lifting fixture, orient the telescope in its parked position (ZD=75), and lift the secondary mirror and cell into the top end of the telescope. Orient the cell with the two locating studs, and attach it to the spacers in the top end with up to 6 1/4-20x0.75 screws (in any case, attach the three screws at the holes with gussets).