The biasing means, such as a compression spring, biases the upper pivotable body 5 to move downward relative to the handle rod 2 so as to permit extension of the upper end 10b of the front rod 1 into the blind bore 5d of the upper pivotable body 5 and so as to abut the lower abutment portion 501 against the upward abutment wall 403 when the conventional foldable rod linkage 3 is in an unfolded pos