Standard writing guides seldom mention the most important mechanical consideration -- proofreading. Because word processors have the ability to turn out a clean-looking page of type, check spellings and perform other routine chores, many students seem to think that these machines have eliminated the need for proofreading. However, computers only catch the obvious mistakes. They do not know the difference between words that sound alike but are spelled differently, such as "their" and "there". By carefully reading over each draft, the author alone can make sure that everything is in order, even if it means correcting mistakes by hand at the last minute. A few handwritten insertions are greatly preferable to a seemingly impeccable copy that turns out, on closer examination, to be full of misspellings, typos, and grammatical mistakes. If you do not know how to spell-check or number pages by using your computer software, then you must be sure to perform these checks manually.