On expeditions we generally have a drill for bolts, failing that for a quick look down a new hole an electron ladder or two (rub does not really matter if you use ladders). Failing that can always put bolts in by hand-bolting. But I have been guilty of myself once on expo, having once descended a tight hole I realised I did not want to go back up. I presumed from looking at our surveys earlier that this hole would connect to the known system below me, which I could exit by. So I took a risk and kept going down despite rub this was creating (Although I had a drill it was not working that day). I had pinned my hopes on the connection being passible and the survey being right. Thankfully they were and I got all the way down by three pitches, dropping some 30m or so on the same rope with a few rocks and stals used as anchors I was out at the bottom made my way back round via the outside world back to the upper cave to reach my bemused companions.