I've bought one of these recently, and it's great.
What is it? It is a clip to make temporary connections to a board with a microcontroller on to program it.
There is a standard pinout for programming Atmel AVR chips, a 6 pin 2x3 pin header with the following pinout. You'll see this on all sort of boards, there's even two of them on an Arduino board.
There are various programmers, from the very simple to the full features ones from Atmel themselves. The one I mostly use is the USBtiny ISP from Adafrruit.
This has an IDC connector on the end of the cable. On the early boards, and ones in active development, I solder a pin header onto the board.
For production boards, I tend to leave the holes in the board.
To program these, I insert the pin headers into the cable.
These will make a good enough connection, if held at an angle for the 10-20 seconds that it takes to program the chip.
And that's how I've been using it for years. I must have gone through half a dozen cables, as the ribbon starts to fray at the edge of the connector.
I have looked around for something to do this better, but most of the things I found need to be added as part of a programming jig. I was looking for something quick and simple. I then saw someone on Tindie selling a 6x1 programming clip.
That looked almost ideal, and I was going to get one as I do have a few boards which use the 6x1 layout with pads on the back, for a production programming jig.
I asked the seller DSTIKE, if they had a 3x2 option, and it they said one was planned, so I ordered one of each.
They arrived very nicely packed, and well protected.
This was just what I was looking for. The clip opens up, you slide it over the edge of the board and it locks in place with the 6 pins in the holes on the PCB.
You can then program the chip without having to hold it in place.
The IDC cable from the programmer plugs into the top.
And there is a clamp at the end so you can hold the wire in place (to stop it flexing and fraying like it used to do).
That's been working really well, so it is now a permanent fixture on my programmer.
The cynical amongst you (i.e. the first person I told about this), could say you could knock something up from a clothes peg. Well, maybe, but this opens wider, has all the connections already in place etc., and wasn't that expensive, so I'm very happy with it.
So, all in all, full marks, if you are interested in something like this, here is the link again to DSTIKE's Tindie store.
Disaster. The plastic on the bottom of the clip has shattered.