A structure , comprising: a first portion and a second portion respectively having a serration (SR) in which peaks and valleys are continuous, and configured to adjust relative positions of the first portion and the second portion in an adjustment direction by interlocking the peaks and valleys with each other, wherein the adjustment direction is a direction in which the peaks and valleys of the serration (SR) are continuous; a fixing portion configured to maintain a defined state, wherein the defined state is a state in which the peaks and valleys are interlocked with each other and the relative position of the first portion and the second portion is fixed; and a positioning mechanism provided on the second portion or the fixing portion , and having a contact portion configured to contact the first portion in the defined state, wherein the positioning mechanism is fixed to the second portion or the fixing portion , thereby making the contact portion contact with the first portion so that the second portion is positioned with respect to the first portion , and wherein the structure is selected from a chuck and a gripping tool, characterized in that the contact portion is configured to contact the first portion in the adjustment direction in the defined state. a first portion and a second portion respectively having a serration (SR) in which peaks and valleys are continuous, and configured to adjust relative positions of the first portion and the second portion in an adjustment direction by interlocking the peaks and valleys with each other, wherein the adjustment direction is a direction in which the peaks and valleys of the serration (SR) are continuous; respectively having a serration (SR) in which peaks and valleys are continuous, and configured to adjust relative positions of the first portion and the second portion in an adjustment direction by interlocking the peaks and valleys with each other, wherein the adjustment direction is a direction in which the peaks and valleys of the serration (SR) are continuous; a fixing portion configured to maintain a defined state, wherein the defined state is a state in which the peaks and valleys are interlocked with each other and the relative position of the first portion and the second portion is fixed; and a positioning mechanism provided on the second portion or the fixing portion , and having a contact portion configured to contact the first portion in the defined state, wherein the positioning mechanism is fixed to the second portion or the fixing portion , thereby making the contact portion contact with the first portion so that the second portion is positioned with respect to the first portion , and wherein the structure is selected from a chuck and a gripping tool, characterized in that provided on the second portion or the fixing portion , and having a contact portion configured to contact the first portion in the defined state, wherein the positioning mechanism is fixed to the second portion or the fixing portion , thereby making the contact portion contact with the first portion so that the second portion is positioned with respect to the first portion , and wherein the structure is selected from a chuck and a gripping tool, characterized in that the contact portion is configured to contact the first portion in the adjustment direction in the defined state. <EOS>