But wait, more of "But wait; more box truck saga"

Back story; centered on hauling items long stored in CA back home. Pick up is full, jokingly relate that volume won't allow more, even room to pour in frozen peas. I bought a converted boat trailer for bulkier stuff, not heavy duty but it is now at 100% capacity volume-wise. Other items to transport in box truck, I rented a 12-footer to transfer from storage to where truck is, far simpler than negotiating workspace at storage.
That rental had an unnoticed feature during the day, until trailer lights turned on.

In the front of either fender (two axles) there is an LED 1/2" jewel lamp, bright enough for use (and sold as) a clearance light. Wired into tail lamp circuit, to me it just confirms the connector between vehicle and trailer is in place, with lights operative. It struck a chord being so useful, mostly an aid cornering or backing up to mind obstructions in the dark, even monitoring position in driving lanes. I never have a spotter, so anything helps.

Well, that multiplies handling the box truck, Without convenient protrusions, the puzzle was how to add the feature narrow-neat-clean-easily. Finally settled on fitting used when installing rigid conduit. It's called a "box extension no holes", covered with blank equal to a switch plate.
Attachment 44181
They're attached on side of the tail and back up housing with the normal 6-32 screws with nuts, not drilled and tapped. Took a minute to fix a position avoiding interference from corners, rounded edges, welds, brackets and plates holding original lights; and passenger side to peek over the lift-gate switch housing. In truth, about a minute for each of those obstructions, times two or more of juggling. I'd say there's an 1/8" of leeway in 2 directions. At home base, would have made a drill guide plate, tapping saves more room than hardware.

Drill 8 holes on a ladder, square and in position, then tap 8 times? No Thank You! Most will agree, using the 6 is least forgiving of all sizes.

Being spliced into parking/ taillight circuit, it is plenty bright to see in mirrors 40+ feet away, even in daylight. Design of lens makes illumination visible 90 degrees off-axis. Watts unknown but "The 2 pk LED 3/4" round red clearance/side marker light meets FMVSS108 requirements for combination clearance.". And the price, at just over $3.00 each, a third less than many others. Hopkins C2534BRK