Systems and methods are provided for positioning and stabilizing an external instrument during insertion of the instrument through the oral cavity (e.g., insertion of a catheter through the oral cavity and into the esophagus or cardia for treatment of gastroesophageal reflux disease (GERD)). The systems and methods provide a gripping tool for association with a bite block, capable of selectively moving between an open position in which the instrument may be inserted or instrument is held in a fixed position.