PURPOSE: To provide a triangle shoe in which an area of the side plate is increased to increase a resistance force against a lateral sliding or a lateral slip and the shoe is pushed into the ground at an accute angle to increase an each of the earth-proof stresses and thereby to enable a stable placement of the power shovel.

CONSTITUTION: Both ends of the bottom plate 3 in the rail steel member 3 used as a railing line are cut at the proper portions to form the steel member with section of substantially I-shape. Then, this I-steel bar is forged to form such a triangular shoe 10 in which its section is substantially V-shape, attachment portions 18 to be installed at the construction development machine are placed at both ends adjacent to a central part of the steel bar, leg bottoms 21 are extended rearwardly at both ends and the concave portions 15 are formed. Attachment holes 20 are made in the attachment portions 18.