If you've learnt about fingerloop braiding, probably one of the first things you learnt was the difference between reversed and unreversed......
Let me explain more about reversed and unreversed pickups. They are respectively pickups where the strands of the loop cross each other (twist) and pickups where they don't. This page and this video provides a nice visual of the difference.
If you want to see this effect in action, Noemi Speiser suggests a nifty method: make a set of linked or departed bowes, with one colour on each side. Arrange them on your fingers so that all of one colour is on the top of your finger on one hand and on the bottom of your finger on the other hand. Start braiding (5 loop patterns are ideal for this) and watch how the colours change. With all unreversed, the colours will all stay on the same side they started on, while with reversed, they will switch every time you exchange that loop.This effect was known to some extent in the medieval era - see the lace bastion.
I'm assuming you probably know reversed and unreversed as picking up the bottom of the loop or the top of the loop. But as well as being able to change which part of the loop is picked up, there are two methods of picking up the loop. With your hands held inwards, in the standard western fingerloop posture (I'm not even going to consider the complexities of other hand postures such V-fell today) your index finger can form a hook that points upwards or downwards.
Let's illustrate that in more detail:
All the standard instruction books I've seen so far assume your hook will be pointing upwards. About 1 in 15 people naturally point their hook downwards. Changing direction your hook points in will change your pickup from reversed to unreversed. Here's a table of possible options:
|hook upwards||hook downwards|
|pickup bottom of loop||reversed/twisted||unreversed/untwisted|
|pickup top of loop||unreversed/untwisted||reversed/twisted|
So, an upwards hook on the bottom of the loop is structurally identical to a downwards hook on the top of the loop. Thus beginning braiders who hook in the less usual direction will get different results from most textbooks. But if they know unreversed and reversed as their motions, rather than learning them as top of the loop and bottom of the loop, they will be able to easily follow textbook patterns. Or if textbook patterns use top of the loop terminology rather than reversed terminology, they will know to swap everything around for themselves, and not be worried about "getting it wrong".
I mentioned 5 loop braids being ideal for seeing the differences in hooking methods. The half circular braid doesn't care whether you pickup the loops reversed or unreversed. Even if the beginner braider switches between reversed and unreversed, they will get a nice result. In some ways this is a good teaching braid because they'll build confidence by getting nice results whichever way they pickup, and can instead work on the 3 stages and tensioning. In other ways, this won't allow them to notice and learn the differences between the different pickups.
The other common 5-loop braids, do care which pickup method is used. It's important for these braids that a braider uses a consistent method of picking up - not for example picking up one side with an upwards hook and the other with a downwards hook, or picking up the top of the loop on one side and the bottom of the other side. The pair of 5 loop braids the round 5-loop braid (beware the diagram is wrong at this link, words are right) and the 2 plaits at once braid differ only by which way they pick up the loops. Using this pair of braids is a great diagnostic to see how another person is picking up their loops, or to test yourself for consistency. Especially if you aim to braid the 2 plaits at once braid, because one single incorrect pickup will re-mesh your two strings together, and be easily noticed.
It's common for a person to switch their hooking direction, for example they may upwards hook the bottom loop and downwards hook the top loop or vice versa. As these moves are structurally identical, they'll need to learn how to control these motions more than your person who only uses one hooking direction, or they will never be able to make more than a few braids. Similarly I find some hooking directions easier on one hand than the other, which can be useful for braids like the flat string, but something I had to train my fingers out of to reliably make the braids I wanted.
Which way was used most in the medieval period?If we look at the English fingerloop patternbooks with which I am most familiar, we can find some clues as to which way looks were "hooked".
The 5 loop round string /pursestring we saw earlier with reversed pickups says to"take all under" while it's unreversed partner the 2 strings at once braid says "takinge the top of the loer fingers alike".These two braids differ only in being reversed or unreversed, and we are quite clear by their titles and the sewn on braid examples of their appearance. In order to pickup the underneath of the loop in the first braid and the top of the loop in the second, and end up with the desired result, both loops must be hooked upwards. So this is a clear indicator of hooking direction used in this set of manuscripts.
However, German recipes for the same braids known in English pattern books, are more flexible about how they pick up loops, as noted by Naomi Speiser. I suspect that while a standard way might have been known, the best fingerloop braiders who created new patterns probably knew this distinction and could use it when it made a complex pattern easier.