Ashley Bend

The Ashley Bend is the name now given to a knot described by Ashley merely by number (ABOK # 1452). It is one in a family of knots based on interlocking overhand knots. It is used to join two ropes of roughly similar size. Testing by Ashley indicated that it was a reliable knot with very little tendency to slip. It can be hard to untie after being heavily loaded.

other references, https://www.animatedknots.com/ashley-bend-knot