My island is full of stone fences marking property or parish borders. Limestone is what the island is made of and it's very easy to get to. You're not allowed to bring it out of the ground yourself, these days you buy it from professional quarries.
Some still use the old techniques to mark their plot boundaries, building a stone wall. The rocks are held in place by their own weight and careful stacking, in this case they even have strings to mark the right hight of the fence. This is a show-off wall, made with great care and planning.
There are two types of stone fences used on the island. Borders are often made like the one you see here, sometimes only two rows, sometimes more, depending on the importance of the wall. Parish walls can be 160 cm high and 60 cm wide. The other kind is a shell-wall, where you stack two parallell rows of big, flat rocks, like the ones you see in the picture, and then fill the in between with little rocks. Those fences are often used in the fields where small rocks constantly come to the surface and then get thrown into the gap between the two rows of rocks.