UKH

I notice that some website's use of this knot for tying into the harness is quite widespread  especially in the EU & the States. It is also used when setting up belays with slings. Yet I can distinctly recall during MIA training years back this knot was a real no no. What has changed?

However I should add that I do use it for attaching a shunt when abseiling (often when used for photographic purposes). Thoughs please.

Is that the one you use when you find that your post-lockdown harness doesn't fit?

Surely it depends on the context? If you're attaching a sewn sling to your belay loop it's probably ok, because even if it halves the strength of the sling you'd really struggle to apply that amount of force anyway. Also, 11kN in a sit harness would cause you severe injuries whether the sling breaks or not. In what situation would it be a problem?

I often tie into the middle of a rope with a girth hitch when using a single on grit. This gives me two ropes for the price of one.

Not sure about tying in, apart from for rappelling and extending your device, which it's more than strong enough for. 

It's come into common use for the 'master point' on belays as it's much, much easier to undo than an overhand.  I think DMM testing showed it to be even better than either a clove hitch or an OH as there's a slight slippage, but not failure, which lowers the load on the remaining anchor.  Seems to be OK with a fair few Guides organizations:

https://www.alpinesavvy.com/blog/try-a-girth-hitch-at-the-master-point

However - to pick a scenario totally at random - it is useless for keeping your wedding ring on a chord round your neck the night before you wedding, when it might fall off in the shower and disappear down the drain.

haven't seen any DMM video on this subject, please link if there is one.

this is the broadest tests I've seen:  youtube.com/watch?v=UMuCkC3jshA& (see 21:31 for girth slippage )

Generally speaking best to have the second do this rather than the leader as it avoids the chance of rope glazing in a leader fall. Apologies if I've read this wrong 😄

I generally tie off with an overhand to stop any slippage.

Maybe not exactly the same as girthing/ larks footing a rope through to give two ropes, a technique I've done before and survived to tell the tale, but it's a good watch to see what relative forces are needed in various sling configurations to break them. 

https://www.youtube.com/watch?v=AsketX8wO9I&ab_channel=HowNOTtoHIGHLINE

Girthed at 13.13 (oooooh, ominous!)

I really like this guy and his testing rig, he does all sorts from carabiners to cams, slings to draws. His presenting style can take a bit of getting used to. 

A Larks Foot.

mmmm I think there maybe an issue in the crushing effect on the belay loop.  Probably a bit extreme 

I also remember a GH being regarded as a weak knot. I use it for fixing my foot in a prusik sling.

I've a German friend (engineer) who sometimes uses it for attaching a sling directly to a wired nut for belay anchors or runners. Again attaching slings to wires with this or other knots used to be a complete no no, and even the lengths of stiff plastic tubing sold on some wired nuts (around late 60s/early 70s?) was said to be useless to prevent the wire cutting through the sling. I think its now thought that tying directly on wire is OK (presumably dependent on wire thickness) though I seem to remember a basket hitch is supposed to be better, though my memory may be at fault.

Yes there was a famous photo of Pete Livesey at Tremadoc with all his wires lark footed! It's obvious that the Rock wire will cut through tape pretty easily. But we were also advised that the Lark's Foot was no suitable for attaching to a fence post for a belay either.

There's a DMM static load test video knocking around somewhere on YouTube - an 8mm sling girthed onto a #1 wire breaks around 7kN.  Not ideal but also approximately the rated strength of the wire.

It's not a no-no. Like any knot it will weaken the rope or sling that it's tied in. By how much depends on how the hitch is set, for example a more 'basketed' hitch is better than one that is very 'choked'. Another factor is the size differential between the hitch fabric and that being hitched around, plus the materials used. For example a thin aramid used around a thicker polyamide could result in failure, and there is evidence of this.

Used sensibly and exposed to only low impact forces ought to be ok.

As you've attracted a couple of comments already with this, my 2p:

It's only slightly more effort to tie into the middle of the rope with a bowline on the bight.  (It involves the same skipping rope manoeuvre, but you then need to chase the slack through the knot as well as your harness.)  Well worth that little bit of extra effort imo.  The bowline is bomber and there's no stopper knot required because there isn't an end to stop.