Editing Slide rule (section)

==Contemporary use==
{{Original research|section|date=February 2015}}
[[File:Faber Castell 6 inch slide rule.JPG|thumb|right|[[Faber-Castell]] slide rule with pouch]]

Even in the 21st century, some people prefer a slide rule over an electronic calculator as a practical computing device. Others keep their old slide rules out of a sense of nostalgia, or collect them as a hobby.<ref>{{cite web|url=http://sliderule.ozmanor.com/srlcol.html|title=Greg's Slide Rules – Links to Slide Rule Collectors|publisher=Sliderule.ozmanor.com|date=2004-07-29|access-date=2010-02-20}}</ref>

A popular collectible model is the [[Keuffel & Esser]] ''Deci-Lon'', a premium scientific and engineering slide rule available both in a ten-inch (25&nbsp;cm) "regular" (''Deci-Lon 10'') and a five-inch "pocket" (''Deci-Lon 5'') variant. Another prized American model is the eight-inch (20&nbsp;cm) Scientific Instruments circular rule. Of European rules, [[Faber-Castell]]'s high-end models are the most popular among collectors.

Although a great many slide rules are circulating on the market, specimens in good condition tend to be expensive. Many rules found for sale on [[:Category:online auction websites|online auction sites]] are damaged or have missing parts, and the seller may not know enough to supply the relevant information. Replacement parts are scarce, expensive, and generally available only for separate purchase on individual collectors' web sites. The Keuffel and Esser rules from the period up to about 1950 are particularly problematic, because the end-pieces on the cursors, made of [[celluloid]], tend to chemically break down over time. [[Conservation and restoration of plastic objects|Methods of preserving plastic]] may be used to slow the deterioration of some older slide rules, and [[3D printing]] may be used to recreate missing or irretrievably broken cursor parts.<ref name="ISRM-Restore">{{cite web |title=Restoring and Repairing Slide Rules and Notes |url=https://www.sliderulemuseum.com/ |website=International Slide Rule Museum}}</ref>

There are still a handful of sources for brand new slide rules. The Concise Company of Tokyo, which began as a manufacturer of circular slide rules in July 1954,<ref>{{cite web |url=http://www.concise.co.jp/eng0731/about.html |archive-url=https://web.archive.org/web/20120312213959/http://www.concise.co.jp/eng0731/about.html |archive-date=2012-03-12 |title=About CONCISE |publisher=Concise.co.jp |access-date=2010-02-20}}</ref> continues to make and sell them today. In September 2009, on-line retailer [[ThinkGeek]] introduced its own brand of straight slide rules, described as "faithful replica[s]" that were "individually hand tooled".<ref name="thinkgeek1">{{cite web |url=http://www.thinkgeek.com/gadgets/tools/be12/ |title=Slide Rule |publisher=ThinkGeek |access-date=2015-04-08 |archive-url=https://web.archive.org/web/20100327174231/http://www.thinkgeek.com/gadgets/tools/be12/ |archive-date=2010-03-27}}</ref> These were no longer available in 2012.<ref name="thinkgeek2">{{cite web |url=http://www.thinkgeek.com/gadgets/tools/be12/ |title=Slide Rule |publisher=ThinkGeek |access-date=2015-04-08 |archive-url=https://web.archive.org/web/20120415123554/http://www.thinkgeek.com/gadgets/tools/be12/ |archive-date=April 15, 2012 |url-status=dead}}</ref> In addition, Faber-Castell had a number of slide rules in inventory, available for international purchase through their web store, until mid 2018.<ref>{{cite web |url=http://service.de.faber-castell-shop.com/epages/es117781.sf/de_DE/?ObjectPath=/Shops/es117781_ServiceParts/Categories/Faber-Castell/FaberCastell_Rechenstaebe |title=Rechenschieber |publisher=Faber-Castell |access-date=2012-01-17 |archive-url=https://web.archive.org/web/20131121041445/http://service.de.faber-castell-shop.com/epages/es117781.sf/de_DE/?ObjectPath=%2FShops%2Fes117781_ServiceParts%2FCategories%2FFaber-Castell%2FFaberCastell_Rechenstaebe |archive-date=2013-11-21 |url-status=dead}} It is believed they may still have some slide rules, but their new website and online store does not carry them.</ref> Proportion wheels are still used in graphic design.

Various slide rule simulator apps are available for Android and iOS-based smart phones and tablets.

Specialized slide rules such as the E6-B used in aviation, and gunnery slide rules used in [[Gun laying|laying artillery]] are still used though no longer on a routine basis. These rules are used as part of the teaching and instruction process as in learning to use them the student also learns about the principles behind the calculations, it also allows the student to be able to use these instruments as a backup in the event that the modern electronics in general use fail.