hold that did not exist naturally is considered acceptable. This is particularly true in some quarries as well as some European crags. However, at many other areas, local ethics absolutely forbid this. Comfortizing holds often involves aggressively cleaning a route to the point where sharp holds have been filed down, often making them somewhat easier to use. While many climbers frown on this, in some areas comfortizing is considered acceptable to a point. Reinforcing rock with glue is the most widely accepted modification to natural features in the sport climbing world. When a popular route is climbed over and over, holds may become looser and closer to breaking. Sometimes, these holds will be reinforced to prevent them from breaking. Other times, if a hold entirely breaks off, it may be glued back on. In most areas, these practices are considered acceptable if done neatly. Sending Sometimes, an ascent or the style in which it is done will come into dispute. For example, a leader who experiences tension on their rope from their belayer while climbing without falling may have not made a valid ascent, through no fault of their own. Additionally, the line between an onsight and a flash is often disputed. Some climbers consider any knowledge of a route, including its grade, to be data that invalidates an onsight. However, other climbers will go so far as to belay another climber on a route and still claim that they did not have enough prior knowledge to move from the onsight realm to the flash realm. Working a route If a climber fails to onsight or flash a route, they may decide to "work" it by attempting to climb it despite falling and hanging on the rope. If, after practising the moves either on lead or on toprope, they manage to lead the route cleanly (i.e. without any rests or falls) then it is called a redpoint. It is known as a 'ground up' ascent if they work the route from the bottom, progressing higher on successive attempts without cheating or resting. However, at popular destinations, multiple parties of climbers will often line up to try a route. A climber working a route may spend an inordinate amount of time on it, preventing other parties from climbing it. This is often frowned upon, particularly if the climber is toproping rather than leading. Not sending a route means that a climber