What is nalbinding?
For nalbinding you need a needle and a piece of yarn, and you make new stitches by inserting the needle through the previous stitches in certain order.
Nalbinding Needle
The needle used for nalbinding is typically a rather large one, flat, blunt, and with a large eye. In Finland the length of nalbinding needles seem to have been most commonly about 8 to 12 cm, but a nalbinding needle can be longer or shorter, too. The width of the needle is usually less than 1 cm at the widest part. Needles are made of wood, metal, or bone, nowadays sometimes also plastic. In Finland the nalbinding needle has been called 'vanttuneula', 'sukkaneula', 'sukkapuikko', 'kinnaspuikko', 'kinnaskokka', and 'kinnastikku' ('vanttu' = mitten; 'sukka' = sock; 'puikko' = needle/pin)
Three main styles of nalbinding in Finland
In the East Finland and the Ceded Carelia* people have known three main ways of nalbinding: 'suomeksi' (by the Finnish way), 'venäjäksi' (by the Russian way), and 'pyöräyttäen' or 'punaltaen' (by turning (or twisting)). In those areas where all three main styles of nalbinding have been known, the Russian style seems to have been the most popular one. These names, though, have not been used outside Carelia although the Russian way of nalbinding has been the most common one in the northern parts of Finland, in the northern Ostrobothnia and Kainuu.
*) "Carelia" is an area which is located partly in Finland, and partly in Russia.
"Ceded Carelia", on the other hand, refers to the part of the Carelia which Finland ceded to Russia after the Winter War in 1940. About 450 000 Finns were evacuated from the Ceded Carelia, and resettled in other parts of Finland. Since the total population of Finland is just barely over 5 millions, many Finns today have grandparents whose roots were in the Ceded Carelia.
"Russian Carelia" refers to the part of Carelia which is located in the Russian side of the border, and has not been a part of Finland (ie it is not a part of Ceded Carelia).
All the archaeological finds in Finland have been made in the Finnish way, and that is thought to be the oldest one in Finland. The Russian way of nalbinding has probably entered Finland from the east, and the youngest of these three main styles of nalbinding in Finland would be the Turning style, which also came from the east.
These three main styles of nalbinding in Finland have had variants, too, so the total count of different nalbinding stitches is higher. Outside Finland, the term "Finnish Stitch" usually seems to refer to the UUOO/UUOOO Stitch (Finnish Stitch 2+2), and the term "Russian Stitch" to UUOOUU/OOUUOOO (Russian Stitch 2+2+2), but here in Finland, both terms 'suomeksi' and 'venäjäksi' cover several stitches, so I would rather talk about the "Finnish Stitch Family" and the "Russian Stitch Family". This grouping in three main styles is based on Ms Toini-Inkeri Kaukonen's nalbinding article in 1960.
In addition to those three main styles, a simpler way of nalbinding has been used e.g. in strainers (photo) of milk sieves (photo).
An incomplete list of different nalbinding stitches (link).
When nalbinding, you hold a needle in one of your hands, and you can use the thumb of your other hand as a tool to regulate the size of the stitches. In some areas in Finland people have been used to drop the newest loop off the thumb, and pick up the stitches/loops onto the needle directly on the front side of the work, while keeping the work flat in front of them, while in some other places in Finland people have preferred to keep the two or three latest loops around the thumb all the time while nalbinding - something that makes the 'weaving' easier especially if the nalbinding stitch type involves several loops.
How to undo nalbinding
Nalbinding belongs to the so called knotless netting techniques, and it is characterized by the fact that you cannot undo nalbinding in a similar way you can undo knitting and crocheting, ie by simply pulling at the yarn. It is possible, however, to undo nalbinding, but that has to be done by pulling the yarn backwards through the stitches/loops one stitch or half a stitch at a time. If there's a hole in a knitted or crocheted item, the stitches easily ladder, but in a nalbound item, the stitches won't ladder in a similar way. An exception to the rule is the Coptic Stitch (Tarim Stitch) which looks a bit like twisted knitting loops. When working with Coptic Stitch (Tarim Stitch), you cannot undo the work like knitting or crocheting, ie by pulling the yarn, but if there's a hole, the stitches may start running from bottom up.