enter image description here I currently have a problem where users are not correctly aligning a plug with a socket on an electrical device, leading to the plug being forced and the pins breaking.

Users have suggested putting a red dot/line on both the plug and the socket to show how the correctly line up.

The questions I have are:

  1. Is red the wrong color to use here (stands out well as the plastic is grey, however could users think 'problem')?

  2. Is there a better (and still easy) way to indicate correct plug & socket alignment?

  • 1
    The "correct" answer is to redesign the plug so that it is inherently obvious; also to design the plug so it doesn't break under a little pressure. Is that a potential option? Do you have a picture of the plug in question that you can post? Feb 11, 2015 at 22:17
  • I agree, unfortunately these are not options at this stage, hence the scramble to provide a quick and easy solution. I've attached a picture. Feb 11, 2015 at 22:48
  • 1
    Is it possible to say 3D print ring caps to go over the socket of the device and on your plug. Create a groove on the ring that goes on the cable plug and a small over hanging lip on the device socket ring that ensures the fit? Seems like you have room on the outside.
    – nightning
    Feb 11, 2015 at 23:44
  • Yes. If you can't redesign the plug, you have to find a way to retrofit existing equipment.
    – dnbrv
    Feb 12, 2015 at 0:09
  • I like the way the Apple Lightning connector and the new USB 3.1 Type C connectors do it - the plug can go in with either orientation and it still works. Lacking that, then aggressive keying of the connector to prevent someone from forcing it together in the wrong orientation is much better than a red dot that may be hard to see if your thumb is over it.
    – Johnny
    Feb 12, 2015 at 1:48

1 Answer 1


Redesign the connector

The obvious, answer if you had the option would be to design the plug so that either:

  • the orientation doesn't matter
  • it's clear which orientation must be used

Modify the housing

If this isn't an option, the next best thing would be to make a modified cover which forces a given alignment. This is could be done by selecting an asymmetrical shape that only has a single 'correct' orientation, or by including some aspect of a shape that stands out and clearly has to fit in a given position for the connector to be inserted. You can see what I mean by looking at the raised top section of the trailer plug and socket below:

enter image description here

Visually mark the orientation

This is typically done with either a red dot or line on the male and female connectors. I can't find an example now, but I've also seen it done with a line on each side with one in blue and one in red - so that a marker is always visible. Ideally I would make the red one a double line and the blue one a single line, and make each tactile by either raising it above or lowering it below the surface.

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