I have a project that uses about 200 solderless jumper wires connecting header posts from one circuit board to the next. Now that the whole thing works, I want to ditch the "temporary" connections in favor of a permanent solution, which means soldering everything in place.
The solderless (female) connectors have a small hole in the side that I'd hoped was there for exactly this reason, but some experimentation leveled a zero, and I'm now in the market for anything that would slide over the header pins and be easily soldered in place. The "temporary" jumper wires I'm using now:
These things are very tightly packed, so I don't have any more room than the jumpers fit in. To be honest, I had to sand a mil or two off of some of them to get them to fit. (They're .1" apart.) =[