The shield was the most common means of defence. The sagas specifically mention linden wood for shield construction, although finds from graves show mostly other timbers, such as fir, alder and poplar with steel or iron shield boss. These timbers are not very dense and are light in the hand. They are also not inclined to split, unlike oak. Also, the fibres of the timber bind around blades preventing the blade from cutting any deeper unless a lot more pressure is applied. In conjunction with stronger wood, Vikings often reinforced their shields with leather or, occasionally, iron around the rim. Round shields seem to have varied in size from around 45–120 centimetres (18–47 in) in diameter but 75–90 centimetres (30–35 in) is by far the most common.
The smaller shield sizes came from the pagan period for the Saxons and the larger sizes from the 10th and 11th centuries. Most shields are shown in illuminations as being painted a single colour although some have a design painted onto them; the most common designs are simple crosses or derivations of sun wheels or segments. The few round shields that survived have much more complicated designs painted on them and sometimes very ornate silver and gold work applied around the boss and the strap anchors.
The Gokstad ship has places for shields to be hung on its railing and the Gokstad shields have holes along the rim for fastening some sort of non-metallic rim protection. These were called shield lists and they protected ship crews from waves and the wind. Some Viking shields may have been decorated by simple patterns although some skaldic poems praising shields might indicate more elaborate decoration and archaeological evidence has supported this. In fact, there is a complete subgenre of Skaldic poetry dedicated to shields, known as "shield poems", that describe scenes painted on shields. For example, the late-9th-century skaldic poem, Ragnarsdrápa, describes some shields painted with mythological scenes. Viking shields were also heavily used in formations. The shield wall or skjaldborg was a main formation in which accomplished Viking warriors would create a line of interlocked shields and thrust spears at adversaries. Other notable tactics included the svinfylking "boarsnout", in which warriors would create a wedge configuration and attempt to burst through the front line of nearby foes.