When climbers descend from long routes, they sometimes need to join two ropes together. This is necessary in order to rappel a full rope length to the next anchor because the ropes are doubled up and looped through the anchor point. Troubles can arise when a climber attempts to pull one line in order to retrieve both ropes to prepare for the next rappel. The knot joining the two ropes could get snagged as it drags against the rock, over edges, into cracks and behind flakes (Baillie, ND-no date provided; Gommers, 2019; Kemple, 2006). A jammed knot might result in entrapment, preventing climbers from descending any farther unless they implement effective self-rescue strategies (Fasulo, 1996; Tyson & Loomis, 2006). Such events have been regularly observed and reported. Knots traditionally used to join two rappel lines together belong to a class of knots inconsistently called one-sided, offset, side, flat or indirect bends. These are knots that afford less resistance when dragged over rock surfaces owing to their shape and relatively smaller contact footprint. It is purported that they have a lower chance of getting jammed in cracks and behind flakes. Accidents have been linked to side bend failures, making them a topic of contention amongst climbers (AMGA & ACMG, 1999; Baillie, No date provided; Baillie, 1982; Chisnall, 1985, 2020; Evans, 2016; Gaines & Martin, 2014; Geldard, 2016; Gommers, 2019; Jackson, 2016a, 2016b; Helmuth & Burnhardt, 2003; Jones, 2012; Kirkpatrick, 2008; Lottman, 2016; Magnuson, ND; Martin, 2009; Martin, 2011; March 1976; Momsen, 2016; Powick, 2016; Prattley, 2016; Prohaska, 1998; Raleigh, 1998; Needle Sports, 2020; Siacci, 2019). Some side bends are more secure than others, although test data and theoretical modelling are not in agreement. The purpose herein is to critically review available information pertaining to these issues.