| 摘要 |
<p>A guide comprising two transparent elongate arms(110,120), each with parallel side edges(111,112,121,122), connected at a right angle to each other at one first end, and each arm having a plurality of a first set of hairlines (115) spaced apart along the length of each arm, the hairlines being parallel to each other and parallel to the side edges of the arm.</p> |
