Knots used in mountaineering
Right from the start it is necessary to mention one important point in order that the use of knots in mountaineering may be correctly understood. The fixing of a knot to a rope reduces the strength of the rope almost in half. Tying knots therefore leads to the degradation of the features of the rope or webbing. For this reason it is necessary to tie knots to a rope judiciously, only in situations when it is critical and brings us some indisputable advantage. The reduction in the strength of the rope is caused by several factors. Above all, in a knot mechanical and thermal (friction) stress occurs as a result of forceful bending around small diameters, which leads to compressing the fibres of the strands of rope on the inside of the bend and stretching the fibres outside the bend. The application of both pulling and pushing tension occurs, caused by the lateral compression of adjacent strands of the rope in the knot. And last but not least, the mutual shifting of the individual structural elements of the rope also contributes to the reduction of strength, from the level of the fibres all the way to the molecular level.
The stronger variant of knot is the one where the load-bearing strand of the rope runs out the top of the knot, that is, as close as possible to the eye formed (in other words, for the strand of rope which we will load immediately after entering the knot to form a curve with the largest possible bend radius inside of it). Also, the more a rope is wound in turns inside a knot, the stronger the knot. The load-bearing strength of a knot is further influenced by how the knot is loaded, whether normally or anomalously.
The various phases of a knot have their own respective names: bight, loop, eye.
Knots can be divided into various groups according to various criteria. A somewhat simple and for mountaineering perhaps optimal classification is into anchoring knots, bends, prusik hitches and handling knots.
Anchoring knots are used for fastening rope. In mountaineering most often to points of protection (e.g. piton, nut, and others equipped with carabiner), or to a harness on the body of the climber when tying in to the rope.
Bends are most often used in mountaineering for joining two ropes together, and for joining the ends of a short piece of rope or webbing, called a sling.
Prusik hitches are used in mountaineering mostly for shinnying along a rope, for fixing (securing) a rope, either when self-belaying or rappelling, or during various rescue processes, such as pulling an incapacitated climber to a belay station, pulling one out of a glacial crack, lowering to an injured party, etc.
Handling knots are somewhat of a special group, serving mostly for handling the rope or influencing rope movement during various operations with it. We can include various stopper knots, shortening knots, so-called slip knots, etc. in this group.