To prevent the post sinking into the ground they are adopted post supports of different shapes and different material.
The oldest polst support is just made up a stone, basically flat, or a brick, placed into the ground under the polst's foot.

They are common concrete supports, round or square. The first one makes a better use of the hole which may be practiced with an auger. The bearing surface is crucial: for an average load it is considered sufficient an area of 300-500 cm2, equivalent to a square of 17-22 cm per side or a round of 20-25 cm of diameter. The post support is also used for the reinforcement of the "rafter" or strut.

These serve to increase the resistance of the head post, which otherwise would tend to bend in the direction of the row due to the pull of the wires. The main advantage of this solution, compared to the anchor system which will be discussed later, is that it does not encumber the service road. By contrast, the resistance is not particularly high, because the tension of the wires tends to undermine the foundation hinging on the same strut.

In particularly friable soils to prevent the collapse of the head post or of the perimeter they  are used to concrete post supports to be then placed in depth where the stakes are then fixed.

The post supports have different sizes and are internally reinforced with a metal structure made of iron.

CONCRETE POST  SUPPORT

As an alternative to the concrete under-post and struts they are used reinforced plates.

They are applied more quickly and easily because they are fixed with bolts to the post already planted in the ground.

COMPLETE REINFORCED PLATES FOR CONCRETE POST

HALF REINFORCED PLATE FOR CONCRETE POST

HALF REINFORCED PLATE FOR WOOD POST