Responses above are correct about needing to take your own hangers (and a spanner) to screw into the spits.
When I started caving only(!) 20 years ago, this was standard practice in all caves that weren't in the CNCC rigging guides of the time (which was nowhere near as extensive a catalogue as it is today). All clubs had a stock of hangers for those kinds of trips. Before the CNCC started anchoring in the early 1990s, it was standard for most caves, even the most popular ones.
It's not surprising that this is an unrecognised concept these days; So many more caves have now been fixed-anchored (thanks CNCC) and of the dwindling numbers of pots still with spits requiring hangers, the threads are knackered.
About ten years ago, when the concept of visiting harder caves appealed to me more than it does today, we had a trip to Newby Moss:
12 photos by Gary Douthwaite
yorkcavingclub.org.uk
The entrance was certainly a struggle, and the first pitch (shown in the photos) was rather snug. However, what thwarted me was a slide down into a small chamber just after the first pitch. This isn't even mentioned as a squeeze in NFTFH, yet try as I might, my rib cage and chestbone wasn't happy. I could have pushed, but I had gravity on my side and so the upward journey would have been hellish. No thanks! There was a small chamber just around the corner where it looked like someone might have (unsuccessfully) tried to dig a bypass.
Yet another trip where I had to console myself with a premature tea and cake at Inglesport.
Definitely one for CNCC anchors if any of the installers fancy it... if I say 'Sam' three times it might happen...
