PROBLEM TO BE SOLVED: To stop a sheet securely without readily transforming a linear member toward the height direction of a groove in perpendicular direction to the dovetail groove bottom face and inhibit that a sheet falls out from a sheet locking dovetail groove readily, by enhancing the flexural rigidity in the groove height direction of the liner member which locks the sheet in the sheet locking dovetail groove.SOLUTION: The present invention consists of one side 11 and the other side 13 in which a central portions 11a and 13a of a linear member 1a extending in the length direction along a groove edge sides 23a and 24a of a sheet locking dovetail groove 2 are curved convexly inward in the groove width direction and the central portion is curved convexly from the direction of the dovetail groove bottom face 21 toward the direction of a dovetail groove opening portion 22, and one oblique side 12 and the other oblique side 14 in which the central portions 12a and 14a curved obliquely obtuse inward in the groove width direction are curved convexly from the dovetail groove bottom face direction 21 toward the dovetail groove opening portion 22. The invention is formed by repeating bending toward the length direction to the sheet locking dovetail groove 2, in the order of one side 11, one oblique side 12, the other side 13, and the other oblique side 14.SELECTED DRAWING: Figure 1【課題】シート係止蟻溝内にシートを係止する線状部材の溝高さ方向の曲げ剛性を高め、線状部材が蟻溝底面に垂直向きの溝高さ方向に容易に変形することなく確実にシートを押し止めて、シートが容易にシート係止蟻溝から抜けて外れるのを阻止する。【解決手段】シート係止蟻溝２の溝縁辺２３ａ，２４ａに沿って長さ方向に延びる線状部材１ａの中央部１１ａ，１３ａが溝幅方向内側に向けて凸状に湾曲し且つその中央部が蟻溝底面２１方向から蟻溝開口部２２方向に向けて凸状に湾曲した一側辺１１及び他側辺１３と、溝幅方向内側に向けて斜め鈍角に曲がる中央部１２ａ，１４ａが蟻溝底面２１方向から蟻溝開口部２２方向に向けて凸状に湾曲した一斜辺１２及び他斜辺１４とからなり、シート係止蟻溝２の長さ方向に一側辺１１、一斜辺１２、他側辺１３、他斜辺１４の順で折り曲げながら繰り返されて形成される。【選択図】 図１
