Abstract: In a woodwind instrument of the type which opens a tone hole by means of the combination of a key and an arm having a tone hole cover at one end both supported by a pair of posts via a hinge rod, a woodwind instrument comprises a pair of bases respectively projecting from the outer periphery of an instrument body and adapted to support a pair of posts. Each of said bases is formed with a hole of sufficient depth so that proper securement of the posts to the instrument body may be obtained upon fitting the lower portion of each of the posts to the corresponding respective hole therein.