X-Acto - No. 9RX Retractable Knife - Carded - The X-Acto No. 9RX Pocket Clip Retractable Knife includes a retractable positive lock blade. This knife is designed for cutting lightweight materials such as film, stencils, paper and cloth. The compatibility of X-ACTO handles with famous X-ACTO blades creates knives so versatile they can accommodate the widest range of cutting requirements. Xacto Number 9RX Knives are pen size for great portability.