shafts 6a and 6b between the reading lever 3a and the retaining hook 5a is disposed a tension spring 7a the reading lever 3a and the retaining hook 5a substantially perform an integral movement on the basis of a principle as will be described later also between the other reading lever 3b and retaining hook 5b is disposed a tension spring 7b and the same operation is performed the numerals 8a and 8b denote positioning stoppers for disengaged positions of the retaining hooks 5a and 5b on the other hand an intermediate portion of a balk 12 having movable hooks 11a and 11b at both ends thereof is pivotably supported at 13 by the fore end portion of a balk lever 10 which is pivotably mounted on another fixed shaft 9 the balk 12 being pivotable around the shaft 13 the movable hooks 11a and 11b at both ends of the balk 12 are supported pivotably relative to shafts 14a and 14b and are engageable and disengageable with respect to the retaining hooks 5a and 5b pushing bars 17a and 17b adapted to pivot in the directions of arrows 15 and 16 through a shaft not shown of the dobby machine which is driven interlockedly with a weaving machine pushing bars 17a and 18b extend in the direction orthogonal to the paper surface that is they extend beyond the balk 12 these bars alternately push the movable hooks 11a and 11b thereby allowing the balk 12 to pivot about the shaft 13 or allowing the balk lever 10 to turn about the shaft 9 when one movable hook is engaged with a retaining hook more specifically.