The word gravestone can imply varying things to different people.
Pertaining to the process of gravestone resetting, we are describing a one piece tablet stone. One piece tablets are monolithic, and are installed is setting them partially underground. The above ground section of stone, which we normally see, may be only one half of the gravestone total size.
Although resetting is not considered a word in any dictionary I have checked, it is most definitely an important part any gravestone conservation project. I have noticed other web sites employ the term gravestone straightening instead, but this is not a fully accurate name for the range of treatments it may describe.
Gravestones set on a grade (hilly terrain), tend to be pushed down hill, very slowly through the forces of soil erosion. Depending on the orientation to the hill, gravestones tend lean forward or backward, or side to side. A forward to backward lean is almost always more acute of a problem.
The greater the lean, and the taller the gravestone, the more critical the condition becomes. Overtime a gravestone with a forward to backward lean, tends to weaken at the point which it enters the ground. Over time, hairline cracks may develop, and in turn lead to breakage. It also becomes a target for lawn mowers as it projects out of the row, making maintenance very difficult.
Gravestones exhibiting a side to side lean may be unsightly, but they are rarely in danger of falling due to simple physics. If they do fall, it is likely to be in very slow motion, without any major damage.
Gravestone resetting may be very simple in theory, but the actually process can be very difficulty. You never know what's underground until you begin the excavation process.
Underground roots, rocks, foundations, and soil conditions can all add up to make a simple task challenging. Larger gravestones may need to be raised with a lifting tripod, in order to reset them properly.
The one most import rule to follow if undertaking a gravestone resetting project is to always dig around the entire stone until the bottom is reached. If a thin gravestone is not excavated fully, when pushed, it is very likely to snap where it meets the ground. Once excavated to its bottom, straightening or raising may be carried out.
In order to free a stone stuck in the ground always pivot from side to side. Never pivot from front to back, especially on thinner gravestones as breakage may result. Once a gravestone has been raised, realigned, and plumbed, a mix of clean sand and pea stone gravel should be carefully placed and packed in around the stone.