Final answer:
During an open cholecystectomy, the Harrington retractor is used to hold back the liver, providing visibility and access to the gallbladder.
Step-by-step explanation:
The retractor used during an open cholecystectomy is the Harrington retractor. This retractor is specifically designed to hold back the liver to provide better visibility and access to the gallbladder during surgical procedures. The Sims, Bennett, and Jennings retractors are typically used for other purposes and are not the optimal choice for an open cholecystectomy. The Harrington retractor's long, flat blade is ideal for retracting the liver, which is necessary in this type of procedure.