A Netgear GS308 gigabit switch replaced an older 100 Mb/s switch below the living room window across from my desk:
Of course, the mounting slots in the new switch didn’t match those in the old switch. A scrap of plastic sheet serves as a space transformer:
The odd-looking knife plows a furrow in the plastic, after which you capture the sheet between two flat surfaces and snap it along the scribe. Faster / easier / more accurate / less exciting than bandsawing, cleans up with quick swipes from an edge deburring tool, not much can go wrong.
The top holes are 3/16 inch for the existing mounting screws. The center holes are tapped 6-32 with nuts to hold them in place.
A block of closed-cell foam behind the sheet holds it vertical so I can just barely see the activity LEDs at each port from my desk.
Yes, I scrubbed the sheet before mounting it…
Memo to Self: put the screw holes slightly higher, so they’re properly centered after sliding the case into position. Otherwise, you must cut another slice off the top of the sheet before mounting it.