Wrapper templates are outer templates which wrap around simpler inner templates, to greatly extend the basic functionality of the inner templates. The concept is to structure the underlying, inner templates to be used as utility tools by various outer, wrapper templates.  Experience has shown that, when the underlying templates have been restructured with a full set of options to be used, then numerous variations of wrapper templates have been created to extend template functionality with a broad variety of new features.  Wrapper templates can be useful for consolidation, as they allow templates to build off of each other, whereas copying and pasting templates can make them harder to maintain.  A simple example The function of Template:Exams is to place a box on one's userpage stating that one is taking a wikibreak to focus on exams. A more general template for wikibreaks, Template:Wikibreak, already exists, so rather than duplicating it,  just consists of a call of  with some parameters specified, such as an image of books rather than the default image of a sunset.  An example with substitution Template:Don't ping inserts a message on a talk page that one is following the page and doesn't need to be pinged in replies. It calls Template:Please ping with the no parameter specified. This gets a little trickier because  may be substituted. To address this, the actual code used is {{safesubst:<noinclude/>Please ping|no}}.  A more complex example One of the most successful applications, of using wrapper templates, has been in extending the features of Template:Convert, which originally could only handle single-value or 2-value ranges of measurement conversions as simple numerals in text. However, once the inner subtemplates of {Convert} were modified to optionally display only the raw values, unit names, or unit symbols, then many wrapper templates were created to handle complex ranges of 4 amounts, with numbers formatted as gapped-digit numerals or spelled-out words:  Template:Convert – the original converter for single or 2-amount ranges  {{Convert/2}} – converter for any range, beyond limits of Convert  {{Convert/3}} – converter for 3-value ranges, not allowed by {Convert} until 2014  {{Convert/4}} – converter for 4-value ranges, with free-form text far beyond {Convert}  Template {Convert/4} could be used to convert 4 amounts at once, as a single thought, such as showing common sizes of lumber for 2 boards at once, or perhaps 2 bedrooms at once:  {{convert/4 |2|x|4|or wide|1|x|6|in|cm}} → {{convert/4|2|x|4|or wide|1|x|6|in|cm}}  {{convert/4 |15|x|18|with 2nd bedroom|12|x|15|ft|m}} → {{convert/4|15|x|18|with 2nd bedroom|12|x|15|ft|m}} Meanwhile, {Convert/spell}, with no complexity added inside {Convert} could display huge numbers, simple fractions, or decimals, all as spelled-out words:  {{convert/spell |67|km|mi}}→   {{convert/spell |67|km|mi|words=out}} →   {{convert/spell |3/8|lb|kg}}  →  Eventually, after {Convert/spell} was refined, {Convert} was rewritten in Lua script with new options "spell=in" or "spell=on":  {{convert|spell=in |1,000.3|m|ft}} →   {{convert|spell=on |7,500,000,000,004|mi|ly}} →   {{convert|spell=on |9|ft|m|frac=10}} →   The formatting of numbers into words is so complex, with so many details, that it took months to spot problems in some particular phrases of larger numbers. If the original {Convert} template had been modified to try displaying the words, or handle 4-amount ranges, then it might have taken years to rewrite {Convert}, and expand all the related thousands of subtemplates, to provide the same level of accuracy as the wrapper templates.   See also   wp:Advanced article editing  wp:Advanced table formatting  wp:Advanced text formatting  wp:Wikimedia Foundation error  wp:Infobox consolidation  Wrapper Templates Category:Wikipedia template help