Extension structure for tool

An extension structure for a tool, comprising:

• an elongated cylindrical joint body having a first end formed with a rectangular locking end, and a second end formed with a mounting portion, the locking end formed with a ball receiving hole for receiving a locking ball, the joint body having a center formed with an elongated central hole, a drive rod slidably mounted in the central hole, the drive rod having a first end formed with an arcuate push recess for receiving the locking ball;
• wherein, the central hole has a distal end formed with a closed wall, a push spring is mounted in the central hole, and is biased between the closed wall of the central hole and a second end of the drive rod, the joint body is formed with a shaft hole that is communicated with the central hole and is directed toward a direction vertical to that of the central hole, the second end of the drive rod is formed with a passage slot that is directed toward a direction vertical to that of the central hole, a rotation control member is rotatably mounted on the joint body, and has a top formed with a knob protruding outward from the joint body and a bottom formed with a drive section secured in the passage slot, and the drive section of the rotation control member has a bottom formed with a circular enlarged head which is passed through the shaft hole and the passage slot, and rested on a bottom wall of the passage slot.