But the theory can also apply domestically.
Months ago one wall of our living room was dominated by custom shelving for about 700 CDs. (Pic above shows 25% of total.) As explained I transferred the CDs to an SD card and now play them through a mini-laptop.
The CDs went up to the attic.
Leaving empty shallow shelves which VR filled temporarily with her collection of little milk jugs.
Then the 18-year-old living room carpet started to wear. But should the replacement carpet be fitted under the CD shelf units (as now) or merely abut them? The carpet, yet to be chosen, will go under the units, which meant an electrician would have to re-position a power socket to make the units mobile.
Meanwhile VR was fed up looking at her jugs as if through letter-boxes. Could we have more depth variety? But the shelves were irreversibly installed as the units were built; removing them by any known method would damage their neatness. Even DIY expert Sir Hugh baulked.
The electrician had an answer. Using a conventional saw UPSIDE DOWN cut a slot up through the middle of a shelf. Then hit the shelf with a hammer. The shelf breaks at the slot and the two halves tear away from the pegs holding them at the ends. Minor damage within the shelves can be disguised with wood-stain.
Did I mention the new audio system plays the TV through the hi-fi loudspeakers? A great improvement.