To easily adjust the tilting of a frame by simplifying the length adjustment of a frame string when adjusting the tilting of the frame by hooking the frame to a wall, especially to match the tilting of at least two frames when hooking at least two frames side by side.

A string-mounting fixture 4 is mounted to either the left or right of the rear of the frame, and a frame string length adjustment instrument 3 is mounted to the other. The end of the frame string 2 is mounted to a string- mounting fixture 4 and a frame string length adjustment instrument 3. The structure of the frame string length adjustment instrument 3 has a string cylinder 6 and a mounting hole 7. The inner diameter of the string cylinder 6 is made smaller than the outer diameter of the frame string 2 for pressing the frame string. The strength for pressing the frame string should be set so that the frame string is moved when the frame string is pulled strongly but the frame can be hooked as it is for retention. The tilting of the frame is adjusted by pulling the frame string from the frame string length adjustment instrument 3 for adjusting the length in the frame string.