I've only managed a very small bit of gear fettling since lockdown began, though I should have done it months ago...
Before Christmas, I decided to buy some trauma shears for cutting dive line with one hand. Having experienced the poor performance of some expensive diving branded shears, I did some reading and one name came up again and again;
X-Shear.
At ?45, the X-Shear is an order of magnitude more expensive than the cheap trauma shears you can get, but comparable to the cost of a shoddy diving branded shear. It is however incredibly highly rated. It is very simple, no extra gadgets, just a pair of scissors, but tough, and cuts through pretty much anything (and apparently keeps on cutting through anything due to the titanium coated blade). If it really was as good as it said, I was prepared to part with the cash and try it out; after all, if it works when you need it to, where an inferior tool would fail, it's worth it.
Having now tested the thing, I can confirm that it really does go through anything, from loose fishing line, to SRT rope with absolute ease; the line does not need to be taught or held with another hand, it just snips straight through, no matter what you point it at.

It also managed some heavy duty twin & earth pretty easily, but fell short of cutting an electron ladder...
The one drawback (other than the price) is that the
tactical holster available for it, does not seem suitable for caving/ diving.
I'd got an idea what I wanted to make, but had not got around to it yet when, the week before lockdown, a friend gave me a bag of old diving bits including a tiny diving knife in a fabric sheath. The knife, nice as it is, seemed little use to me, but the sheath fitted the shears perfectly. However, the securing band was in the wrong position to hold in the shears.
So my gear fettle was to unpick and re-stitch the securing band at a jaunty angle, using my Speedy Stitcher. For those who don't know what this is, or don't own one, just go and buy one and try it out. An absolutely brilliant bit of kit for sewing tough fabric; pays for itself in a few oversuit patches, but also good for making caving belts, fixing tackle bags, re-stitching the hood on your vintage car, or whatever else you need to sew
Unfortunately the heavy duty nylon thread I have is white and the sheath is back, so it looks a bit crap, but with the shears in, you can't see the stitching anyway.
The final touch was to add a couple of bungee loops so it can be worn on the arm.
The result seems very good and is easy to operate with one hand in thick diving gloves, though I'm yet to see how easy it will be with frozen hands as well...