To improve the accuracy of a contact part as a reference position relative to a groove position, regarding a rule used for marking a drilling position on a wooden material.
Plates 3 and 4 are fixed to the upper and reverse sides of the upper part of a flat area 2, and plates 5 and 6 are fixed to the upper and reverse sides of the left part of the flat area 2. Also, a cross groove 7 made of vertical and horizontal grooves 8 and 9 is formed on the flat area 2 at three positions, and when a layout line 30 is marked on the left end of a wooden material 23, the lower side 3a of the plate 3 and the lateral side 5a of the plate 5 are made to collide with the wooden material 23. When the layout line 30 is marked on the right end 23 of the wooden material 23, a rule 1 is rotated in right and left directions, and reversed, thereby keeping the reverse side 2d of the flat area 2 at an upper position. Then, the lower side 4a of the plate 4 and the lateral side 6a of the plate 6 are made to collide with the wooden material 23.