Anathyrosis is the technical word for the ancient method of dressing the joints of stone blocks in dry stone construction, i. e., masonry without mortar, which was then commonly used.
Anathyrosis is a finely processed surface of the stone block, which serves as a proper blocking of the blocks, and for the purpose of transferring force to the edges of the block, which increases the high pressure.
Because the stone blocks are set in immediate contact with each other without gaps, their joints must be exactly dressed. In order to reduce the time required to sculpt such joints, the faces of the stones to be joined were finished and smoothed only in narrower margins on the sides and top of the faces to be joined, while the interior of adjoining faces were recessed. The smoothed margins of such a face together resemble a doorframe, and the word, created by the ancients, is allusive.
Thyra (θύρα) is Greek for “door”, and thus “door framing” is anathyrosis. This technique was frequently used to construct walls, including in ashlar form, and was used to join the drums of columns. Close examination of where this technique was applied to a specific stone block since removed or fallen away can help locate its placement in the edifice or determine whether it was joined to other blocks.
The area on which the blocks are interconnected is often slightly loosened, and finely trimmed on the edges, which forces the forces from the center of the block to be transferred to their edges. This, however, increases the risk of fracture of the treated stone blocks. The technique is particularly commonly applied to sharp fractures.
In later periods, especially from the 1st century AD, Furthermore, an anatomy is increasingly pronounced and made more smoothly by a fine stencil, which gives the wall surface a dynamic effect of chiaroscura.
In the end, the wall face receives two plans: deeper-shaped stone stitch anatodes (slags), and surface shaped by protruding blocks of blocks that are generally in the same plane.
Source From Wikipedia