Derailleur gears several standards in use, and in each the product of the derailleur's actuation ratio and the length of cable pulled must equal the pitch of the rear sprockets. The following standards exist. Some rear derailleurs, especially for mountain bikes, incorporate a clutch to keep the lower length of chain in sufficient tension to prevent the chain from striking the bottom of the chain stay, called "chain slap", and which can damage the chain stay. Clutches are also helpful in preventing the chain from derailing from the chain ring on systems without a front derailleur. The front derailleur only has to
Word sort to help students who do not have extensive reading vocabularies focus on isolated sounds (Initial, final, or medial) within a spoken word. These sorts are often a child’s first introduction to word study and are most commonly used with students whose developmental skills are at the emergent, letter name-alphabetic, or early within word Spelling Stages. Word sort activities involve students comparing, contrasting, and classifying words - considering words from a variety of perspectives. Bear et al. emphasized the importance of comparing those words that do fit into a particular category with those that don't. This type of engagement with words