Reef Knot - is a simple knot used to securely join two ends of a rope of equal thickness together, making it ideal for situations where you need to tie something firmly but still be able to easily untie it later; it’s commonly used in sailing to “reef” sails by reducing their surface area, hence the name “reef knot”. Function: Primarily used to join two ropes together, creating a flat, secure connection. Applications: Sailing: Reducing the size of a sail by tying parts of it together (“reefing”)