The short Seax is also known as a Scramasax, a Hadseax or just a Sax. The term Scramasax comes from Gregory of Tours writing in AD 575, who speaks of "boys with strong knives (cultris validis), which they commonly call scramasaxes (scramasaxos)." in his History of the Franks (IV, 52). It is not known if this name continued in use into the Viking Age.
It is not uncommon for burials in the Viking age to contain more than one knife. It is likely that small heavy seaxes were in use up until the end of the C10th but that as a weapon it possibly really belongs to the pre-Viking period.
Although primarily an everyday tool, in battle it could be used to finish off a felled opponent, and in the case of some ceorls, a mid to large sized scramaseaxe could have taken the place of a sword. Although it contained much the same amount of iron to make as a sword, the scramaseaxe was an easier weapon to make with only one sharp edge and a thick reverse edge. Examples found have both just plain iron blades or pattern welded ones as well as inlaid blades.
Seaxes were also almost certainly just everyday tools: butchery knives, woodworking tools, eating knife, etc.. Most blades were broad, heavy and with an angled back sloping in a straight line towards the point and this is the typical Saxon style.
The Scandinavian style had a more curving back and the Frankish style a more curving blade. Blades were often inlaid with gold, silver, copper or bronze wire beaten into fine channels carved into the iron blade. The grip was of wood, bone or antler and was sometimes carved or decorated. The hilt was usually without a pommel or crossguard, whilst the tang went all the way through the smaller seax handles and was clenched over at the end of the grip.
Scramseaxes were always carried in a sheath of folded leather sewn down the blunt side of the blade, which was often decorated. It is unlikely that a small scramaseax could kill a heavily padded or mailed man, probably just serving to irritate him. It's main employment was probably as an eating and all-purpose 'pocket' knife. The blunt reverse edge of the seax could be used as a hammer to break bones to extract the marrow, or even hammered through materials via it's blunt back as a sharp wedge. It also gives a lot of strength to the whole knife.