Abstract: An apparatus for tying knots can include a body defined by a length along a longitudinal axis of the body and by an outer surface that extends around the longitudinal axis of the body from a first end of the body to a second end of the body. A trench in the body can extend from the outer surface of the body toward the longitudinal axis for the length of the body. A channel can extend for the length of the body and is exposed at the first and second ends of the body. A neck can be between the trench and the channel, the neck can be configured to contain first and second flexible lines extending in the channel extending from the first end of the body to the second end of the body and a line guide can be on the outer surface of the body configured to hold the first or second line at an oblique angle relative to a direction of the longitudinal axis.