<Li> Discrete, discernible "edges" that are formed by being completely separated from the surrounding surface as in 1 and have boundaries dictated by the limit of excavation . </Li> <P> Following this preliminary process of defining the context, the context is then assessed in relation to the wider understanding of the site, for considerations of reduction of the site in phases, and then removed and recorded by various methods . Often, owing to practical considerations or error, the process of defining the edges of contexts is not followed and contexts are removed out of sequence and un-stratigraphically . This is called "digging out of phase". It is not good practice . After removing a context or if practical a set of contexts such as the case would be for features, the "isolate and dig" procedure is repeated until no man made remains are left on site and the site is reduced to natural . </P> <P> The process of excavation is achieved in many ways depending on the nature of the deposits to be removed and time constraints . In the main, deposits are lifted by Trowel and Mattock and shovelled or carried from the site by wheel barrow and bucket . The use of many other tools including fine trowels such as the plaster's leaf trowel and brushes of various grades are used on delicate items such as human bone and decayed timber . When removing material from the archaeological record some basic guidelines are often observed . </P> <Ol> <Li> Work from the known to the unknown . This means that, if one is unsure of the stratigraphic boundaries of the material in question, the removal of material should start from an area where the sequence is better understood rather than less . </Li> <Li> Work from the top to the bottom . As well as working from the known to the unknown, also as far as possible, remove material at the physically highest level in the context and work towards the lowest . This is best practice because loose spoil will not then fall onto and contaminate the surface being worked on . In this way blurring detail that might have been instructive to the excavator is avoided . </Li> <Li> In archaeology, we use our eyes . Excavation of contexts correctly often relies on detailed observations of minute differences . </Li> <Li> If in doubt, bash it out . This rather cavalier - sounding maxim is a concise way of expressing the need to progress . There is always more to be done on a site, than there is time in which to do it . At times the next feature or context to be removed in the sequence is not clear even to an experienced archaeologist . When it is not possible to proceed in an ideal manner, the excavation must be continued in a more arbitrary way, with temporary sections, until discernible stratigraphy is again encountered . An area of the site is reduced leaving arbitrary, temporary sections as a form of stratigraphic control to provide early warning of "digging out of phase". If the arbitrary area for excavation is wisely chosen, the sequence should be revealed and excavation can return to a truly stratigraphic method . It is important to realize that "bash it out" is not a totally random act but a best guess based on logical deductions, observation and experience . </Li> </Ol>

Name two instruments which an archaeologist would use to excavate a site
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