The second set of closet doors we got from the Covington Reuse Center were for the 3rd floor closet. This closet is 60" x 8o". We picked up 2 white 2-paneled hollow core doors for $15 each.
Problem #1: The doors were 30"x 84". (4" too tall.)
Problem #2: The sliding door track and rollers require 1-1/2" of additional space to handle the doors.
Problem #3: the solid part of the exterior of the hollow core doors are only solid for 2-1/4" in.
Hence, if I cut the door to fit at the top and the bottom, there will be only hollow 1/8" exterior paneling left, and no solid wood at the top and the bottom of the door. Like this:
So I cut 1-1/2" from the top, leaving enough solid wood to attach the track wheels to the top. (They are attached at the top 1/4" anyway.)
And then cut the rest off of the bottom of the door. Leaving, of course, a hollow shell of a door at the base, and a remnant of what used to be the solid base to each door.
So I took the cut off remnant (chunk that was cut off the base of the door) and I chiseled off the 1/8" exterior paneling and the solid wood side pieces from the door frame sides (all of the grey, leaving the solid wood piece.)
The cut off piece looked a little like the above sketch, wherin the light grey is the paneling, the darker grey is the side panel wood, and the brown area is the solid wood. Once all of the paneling and extra wood is chipped off (and planed - these are attached with wood glue) the solid wood piece could then be glued, stuffed and clamped back into the hollow area at the bottom of each door again.
It's a perfect fit.