Things you have never learned how to do.

[ebikeerwidnes]

Welding or its much easier cousin, soldering.

We had WoodWork/metalwork lesson in school
I was terrible at woodwork - never got the measurements right and was incapable of cutting in a straight line
but metalwork was OK
we did some soldering - the type with a flame and all that and I was OK at that

but I worked in IT for many years and some soldering was sometimes needed
my boss would not let me anywhere near a soldering iron -- he knew I was dangerous with wires and an soldering iron!!!
I just cannot hold my hand still - it always trembles a bit especially if I am concentrating - so any cable I soldered would probably have several contacts soldered together rather than just the ones that were needed

 

[Andy in Germany]

We had WoodWork/metalwork lesson in school
I was terrible at woodwork - never got the measurements right and was incapable of cutting in a straight line
but metalwork was OK
we did some soldering - the type with a flame and all that and I was OK at that

but I worked in IT for many years and some soldering was sometimes needed
my boss would not let me anywhere near a soldering iron -- he knew I was dangerous with wires and an soldering iron!!!
I just cannot hold my hand still - it always trembles a bit especially if I am concentrating - so any cable I soldered would probably have several contacts soldered together rather than just the ones that were needed

We had a metalwork section during my cabinetmaker's apprenticeship. After a few days one of the group went to the carpentry master and said: "Whatever we did to upset you, we're sorry, can we come back now?"

 

[Profpointy]

Welding or its much easier (to do) cousin, soldering.

I did a MIG welding course fairly recently and enjoyed it and though I'm unlikely to do much with it got quite a lot out of it. 3mm mild steel is a lot easier than thin sheet like car panels which we also had a go at.

Got a chance to play with a TIG machine after we'd done all the city & guilds test pieces. Though it was harder if anything it was very satisfying and TIG is hell of a lot more versatile so I'd likely go for a TIG machine if I ever buy one. (basically you can weld most materials with just argon, and the right filler rods. For MIG you'd need a a whole spool of each type of filler wire and different gases and cylinder rental is a big cost)

 

[Profpointy]

Solder copper pipe. I've done.lots of DIY plumbing over the years but its always been out of sight for the most part..so compression fittings were always the 'safe' option

My first attempt at this was a genuine triumph. There was a burst pipe on an ascot at our caving club, but as we didn't exactly have spares I had to solder a half inch pipe to a 3/4 pipe. Not expecting success, I managed to gradually fill the huge gap with solder making a watertight join!

 

[Profpointy]

I also have never been able to do things like track stands or ride no hands.

Riding no-handed is very bike dependant. I really can't do it on my Thorn tourer but it's easy on my Condor fixie, which has the same frame as their audax model so almost a touring bike shape