Hedman & Costigan P.C.
Writing instrument
 A writing instrument includes a hollow barrel having a longitudinal slot defined through the barrel. The slot has two sides, and a series of continual indentations are formed in each side. A connecting device is slidably mounted in the barrel. A thrust device is mounted on the periphery of the barrel to drive the connecting device. The connecting device includes two opposite ends with a hollow, cylindrical connector attached to each end to connect to a crayon, a colored pencil or an eraser stick. Consequently, the writing instrument is easy to operate, never dirties the user's hands and can be used as an eraser or a double-color drawing pen. 
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Wen-Yi
Wang