When will the frontier defense be erected?

Set up within half an hour before construction. According to the relevant regulations, when the falling height datum is 2m or above, protective railings should be set on the limb side, and limb protection should be set half an hour before construction. Erection of limb protective railings should be composed of upper and lower rails and railings. The upper pole height is 1.2m, and the lower pole height is 0.6m ..