| 摘要 |
According to the present invention, since an upper surface of a tread is formed of a horizontal portion extending from a central portion to side portions or inclined portions inclined downwardly from side portions or another inclined portions extending from both ends of the horizontal portion or the inclined portions at the angle ranging from 1 to 5 degrees, it enables operators to put their feet on a tread in a more natural state to move up and down under a stable condition, and to reduce their fatigue with their feet or knees when they move up and down in a manhole utilizing the foothold. To this end, in the foothold of the manhole the tread (5 or 23) and side portions (6 or 24) extending from and positioned at both sides of the tread (5 or 23), wherein at least an upper surface of the tread is formed of a horizontal portion (11) extending from a central portion (S) of the tread toward side portions thereof, inclined portions (27) inclined downwardly toward the side portions or inclined portions (12 or 28) inclined upwardly from both ends of the horizontal portion or both ends of the inclined portions (27) at an angle ranging from 1 to 5 degrees. <IMAGE> |
