Gatehouse
Any building housing a gate or sets of gates that could be barred or locked against outsiders. All periods have used these, from Iron-Age hillforts, through Roman forts and towns, Saxon burhs, medieval manors, castles and towns to more recent forts of Georgian and Victorian times.

Geophysics
A group of geophysical techniques are now available to archaeologists and others to help them find sites. The most common are magnetometry and resistivity. In the former, the earth's magnetic field is measured together with any effects that structures in the ground may have on it. Walls, pits and trenches can all affect the readings, and these can then be plotted out, producing a sort of underground or subsurface map of features not always visible on the ground. With resistivity, the electrical resistance of the soil and any buried features in it is measured: where there are buried pits and ditches, there is little resistance, whereas walls and stone give great resistance.

Ground-penetrating radar may also eventually prove a very useful technique for archaeologists. It can examine deep deposits (ie some metres down), such as those found in towns, and initial results have been spectacular. As yet, however, the interpretation of the signals seems to be a difficult process.

No doubt other geophysical techniques will be developed, and the location of archaeological sites, where there is nothing to see on the surface, will become more common. This is one of the most exciting areas of archaeological research and development.

Glass
Although there is some Roman, Saxon and medieval glass, and window glass from the Roman period has been discovered, most of the glass found is post-medieval (after 1550) and its relative abundance relates to the increasing use of bottles. These gradually developed in shape from squat, wide, thin-necked pieces to the more familiar wine bottle shape of today. Buried in the ground, glass often weathers to produce a patina of iridescent colours, very different to the green or brown with which we are familiar.

Gold
A metal which seems to have been regarded as precious since its first use in the early Bronze Age, probably because it does not tarnish and as one of the few free-standing elements found in nature it does not need to be extracted from rock. When discovered on sites today, gold (and silver) objects are subject to the laws regarding treasure trove and their fate has to be decided in a coroner's court.

Grass tempering
All clay used in potting has to have a 'temper' added to assist it to dry without cracking and to help with firing so the pots do not explode. Very many things have been used as temper in the past, such as grit, crushed limestone and shells, and sand, and which material has been used is often a clue to the date and area of the manufacture of the pottery. One of the most distinctive is temper made from chopped-up grass, straw or chaff: when the pot is fired, this vegetable matter burns away, leaving distinctive voids. This type of pottery was common in the late Roman and early Anglo-Saxon periods, c 350-700 AD.

Grids
Excavation used to be conducted in a series of grids, but small trenches or large areas are now preferred. However, fieldwork is still often carried out by gridding a field in 10-, 20- or 50-metre squares and collecting from those areas. Geophysical survey is usually conducted within grids as well.