To solve such problems that a conventional ruler has shortcomings such as being not handy for positioning and easily movable when a side line is drawn to printed characters of a book or the printed characters are colored, and the ruler itself easily slips or difficult to fix, when the side line is drawn to the printed characters near a bound part of a vertically printed book or the printed characters likewise near the bound part are colored, and the ruler for drawing the side line or for coloring the printed characters cannot be carried by inserting the ruler into the book, whenever such portability is desired, because there is the possibility that the ruler might slip off.

A folded-back piece with a folding width of a few mm is formed by folding one end of the ruler at right angles, and secured to the upper end part of the book to move the folded-back piece in parallel. Thus the unnecessary movement of the ruler is checked. In addition, when the side line is drawn to the printed characters near the bound part or the printed characters likewise near the bound part are colored, the folded-back piece is secured to the upper end part of the bound part and the ruler is fixed to perform the required procedures. Besides, it is possible to carry the ruler by inserting the ruler into the book after fastening a soft, transparent vinyl sheet-like securing implement to one end of the ruler and securing the implement to a sheet laminate of the book. Further, the sheet-like securing implement can be used as an automatic bookmark to be inserted into the book.