Often on sites with a large number of post holes the supervisor or Site Director will have the diggers (should be referred to as Excavators or Site Assistants really) stand in the excavated post holes and a photo is taken. This isn't as difficult as it sounds as many ancient post holes of large structures can be up to a metre across. The idea is to effectively show the pattern and thereby illustrate the outline of the "lost" structure. The problem is in the life of a site with later structures being built or alterations and additions to a structure, not to mention sites being re-used, you end up with more post holes than you can shake a stick at! Discerning any underlying pattern can send you quietly mad., with no certainty that what you think you have found is really there - to give you an idea, I'm still hoping to find the Hanging Gardens of Babylon, not necessarily in the Middle East.
Post holes are first 'sectioned' - half the hole excavated with the remaining half presenting a face one which can (hopefully) be seen tip lines, and sediments etc. Whilst still a student (c.1992) I returned to a dig in Yorkshire (yet again) from a dig in Shetland with what I think is described as a frozen shoulder (locked and agony to move). The trench supervisor left me in a corner on my own to dig , very slowly, a large medieval post hole, roughly rectangular, about0.75m a side and eventually nearly 1 m deep. Kneeling over the hole with one arm tucked in my shirt (in pain) precariously reaching down to trowel with one arm meant for very slow progress indeed! After 2 days (!) I found myself kneeling head into hole crying -but had to work as I needed the money.
Which brings me to the 'constant' of archaeology -beer! That night on the advice of a friend (?) I was drinking Thunderbird and stout mixed. After 2 pints and 4 cans of lager I was reduced to crawling on all fours and mumbling, and in those days I could hold my beer! The following morning I was as they say "right as rain", no shoulder problems and no pain, and even no hangover! The remaining half of the post hole, including drawing the section took me half a day to finish and life restarted.
Personally I've never worked on a site with a clear pattern of post holes, but have always found beer readily available (outside of working hours I might add) and usually in large quantities. Could perhaps the lack of ability to recognise a discernible pattern be related to beer I wonder. And please no lectures, I am today virtually tee total (well except for when 'digging').