To provide a boundary property and an expression of a space and enable construction of the space itself by forming a gatepost in combination of basic parts and joint parts to constitute the gatepost for a house.

Two basic parts 20, 20 are erected and joint parts 21, 21 are connected to the upper ends of the basic parts 20, 20 respectively to lay a basic part 20 between the joint parts 21, 21. In this way, the basic part 20 and the joint parts 21 are combined to form an arcuate gatepost 3. Since the basic parts and the joint parts enhance usability, these parts are used as common members, therefore, flexible constitution can be obtained by appropriately varying the combination of the basic parts and the joint parts, hence, various expressions are enabled.