The knot used to join two lines of different diameter is a __________.

The becket bend is specifically designed for joining two lines of different diameters, making it an effective choice in various maritime and boating applications. This knot maintains stability and security when used on ropes that may not match in size, which is critical when securing loads or connecting equipment on a vessel. Its structure allows for easy tightening and is less likely to slip compared to other knots, thereby ensuring reliability during use.

The other knots mentioned serve different purposes: the square knot is used for tying two ropes of similar size together, the carrick bend is excellent for securing larger lines or heavy loads but may not be as effective for different diameters, and the sheepshank is used primarily for shortening a line without cutting it and does not join two lines together. Understanding the appropriate applications for each knot is essential for safe and effective boating practices.