During the Viking age warriors used round wooden shields gripped in the center from behind an iron boss. Typical shields were 80-90 cm in diameter, some were smaller down to 70 cm or larger up to 94 cm.
Shields are made from spruce, fir, pine or linden planks butted together. Most have a single layer of boards and some have a double layer. The normal thickness of a shield lies between 6 and 12 mm, but some were much thicker. The center of the shield is thicker then the edges in most cases twice as thick.
At the center of the shield there was a domed iron boss, which protected the hand. A typical boss was 15 to 16 cm in diameter with a thickness of 3 to 5 mm. There are many variants in shapes and forms. Some have a neck and knob which were probably used in special maneuvers e.g. to disarm the opponent.
The shield was probably rimmed with leather. rawhide or iron to keep the shield from splitting when hit on the edge. A common practice was to use a leather sling to carry the shield over the shoulder.
Some shields would have been faced with linen, held in place with hide glue to strengthen the wood. Also many shields would have been sealed with oil to repel water. A shield that soaked up water from rain or sea spray could easily double in weight, becoming so heavy and waterlogged as to be nearly useless.
Source: Hurstwic: Viking Shields
The attributes of the kite shield are different from other items. The attack is reduced by two points, but the defense is up by three points. The item is wielded with one hand and can be used in all distance classes. A kite shield is not cheap and is used mostly by horsmen and heavy infantry.
In battle a shield is invaluable in small- and large group formations like the shield wall. Also a number of special maneuvers are attributed to the shield giving it an all-round use.