What is the best knot to use when joining two ropes of unequal diameter?

Using a sheet bend is the best choice for joining two ropes of unequal diameter because this knot is specifically designed for that purpose. The sheet bend effectively secures the thinner rope to the thicker rope by allowing for a snug fit, which prevents slipping. It accommodates the varying diameters well, ensuring a strong connection even when the ropes are of different sizes.

The sheet bend is particularly advantageous because it is easy to tie and untie, which can be beneficial in situations where the knots may need to be adjusted or released. Additionally, it is less likely to come undone compared to some other knots when under load, making it reliable in various applications.

In contrast, other knots such as the clove hitch, timber hitch, and sheepshank are not as effective for connecting ropes of different diameters. The clove hitch and timber hitch are more suited for securing a rope to a post or object, while the sheepshank is intended to shorten a rope without cutting it. Therefore, the sheet bend is the optimal choice for this scenario, ensuring a secure and reliable connection between two ropes of unequal thickness.