The simple task of cutting a hollow-core door to height can become much more difficult if you have to remove more door than the bottom plug allows. Until recently, I always used to cut a new plug. I then would remove enough of the cardboard honeycomb between the veneers to accommodate the new plug, and glue and clamp it into place. This could become a time-consuming process, especially if there were several doors to be modified.
On a recent job, I decided to try a new approach. After cutting a hollow-core door to height, I sprayed a minimally expanding window-and-door foam into the bottom of the door. I trimmed the cured foam the next day, sealed the door bottom with primer (the door was to be painted), and installed the door. I have since used this method on a couple of other jobs, and it has produced fast, consistent results.
Michael Dexheimer, River Falls, WI