Editing Curling (section)

=== {{anchor|Curling sheet}}Curling sheet ===
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[[File:CurlingHouseAndBackline.svg|thumb|Detail of the curling sheet. The 12-foot circle covers the backline.]]
The playing surface or ''curling sheet'' is defined by the [[World Curling Federation]] Rules of Curling.<ref name="Rules">{{Cite web |date=October 2022 |title=The Rules of Curling and Rules of Competition |url=https://worldcurling.org/competitions/rules/ |access-date=2023-06-15 |website=World Curling Federation}}</ref> It is a rectangular area of ice, carefully prepared to be as flat and level as possible, {{convert|146|to|150|ft}} in length by {{convert|14.5|to|16.5|ft}} in width. The shorter borders of the sheet are called the backboards.

A target, the ''house'', is centred on the intersection of the ''centre line'', drawn lengthwise down the centre of the sheet and the ''tee line'', drawn {{convert|16|ft}} from, and parallel to, the backboard. These lines divide the house into quarters. The house consists of a centre circle (the ''button'') and three concentric rings, of diameters 4, 8, and 12 feet, formed by painting or laying a coloured [[Vinyl composition tile|vinyl]] sheet under the ice and are usually distinguished by colour. A stone must at least touch the outer ring in order to score (see [[#Scoring|Scoring]] below); otherwise, the rings are merely a visual aid for aiming and judging which stone is closer to the button.
Two ''hog lines'' are drawn {{convert|37|ft}} from, and parallel to, the backboard.

The ''hacks'', which give the thrower something to push against when making the throw, are fixed {{convert|12|ft}} behind each button. On indoor rinks, there are usually two fixed hacks, rubber-lined holes, one on each side of the centre line, with the inside edge no more than {{convert|3|in}} from the centre line and the front edge on the hack line. A single moveable hack may also be used.

The ice may be natural, but is usually frozen by a refrigeration plant pumping a [[brine]] solution through numerous pipes fixed lengthwise at the bottom of a shallow pan of water. Most curling clubs have an ice maker whose main job is to care for the ice. At the major curling championships, ice maintenance is extremely important. Large events, such as national/international championships, are typically held in an arena that presents a challenge to the ice maker, who must constantly monitor and adjust the ice and air temperatures as well as air humidity levels to ensure a consistent playing surface. It is common for each sheet of ice to have multiple sensors embedded in order to monitor surface temperature, as well as probes set up in the seating area (to monitor humidity) and in the compressor room (to monitor brine supply and return temperatures). The surface of the ice is maintained at a temperature of around {{cvt|23|F}}.<ref name="branch">{{cite news |url=https://www.nytimes.com/2009/08/17/sports/17curling.html |last=Branch |first=John |title=Curlers Are Finicky When It Comes to Their Olympic Ice |work=The New York Times |date=17 August 2009 |url-status=live |archive-url=https://web.archive.org/web/20171006062707/http://www.nytimes.com/2009/08/17/sports/17curling.html |archive-date=6 October 2017}}</ref>

A key part of the preparation of the playing surface is the spraying of water droplets onto the ice, which form ''pebble'' on freezing. The pebbled ice surface resembles an orange peel, and the stone moves on top of the pebbled ice.<ref>{{cite press release |url=http://www.twincitiescurling.org/press_release/usa_today_021704.html |title=USA-Today: Curlers Play Nice and Leave No Stone Unturned |publisher=Twin Cities Curling Association |url-status=dead |archive-url=https://web.archive.org/web/20120902063305/http://www.twincitiescurling.org/press_release/usa_today_021704.html |archive-date=2 September 2012}}</ref> The pebble, along with the concave bottom of the stone, decreases the friction between the stone and the ice, allowing the stone to travel further.<ref>{{Cite web|url=https://www.smithsonianmag.com/innovation/why-curling-ice-is-different-than-other-ice-180949752/|title=Why Curling Ice is Different Than Other Ice|last=Hendry|first=Erica R.|website=Smithsonian|language=en|access-date=2019-05-10|archive-date=10 May 2019|archive-url=https://web.archive.org/web/20190510182636/https://www.smithsonianmag.com/innovation/why-curling-ice-is-different-than-other-ice-180949752/|url-status=live}}</ref> As the stone moves over the pebble, any rotation of the stone causes it to ''curl'', or travel along a curved path. The amount of curl (commonly referred to as the ''feet of curl'') can change during a game as the pebble wears; the ice maker must monitor this and be prepared to scrape and re-pebble the surface prior to each game.<ref>{{cite web |url=https://www.nbcnews.com/id/wbna35537168 |title=Smooth operators: They make Olympic ice nice |date=23 February 2010 |publisher=[[MSNBC]] |work=Today in Vancouver |url-status=live |archive-url=https://web.archive.org/web/20121004155357/http://today.msnbc.msn.com/id/35537168/ns/today-today_in_vancouver/t/smooth-operators-they-make-olympic-ice-nice/ |archive-date=4 October 2012 |access-date=12 August 2011 }}</ref>

{{wide image|Curlingsheet flip.svg|800px|3=<div style="text-align:center;">A curling sheet, with dimensions in feet (<nowiki>1' = 1&nbsp;ft = 0.3&nbsp;m</nowiki>).<br/>'''CL:'''&nbsp;Centreline{{•}} '''HOL:'''&nbsp;Hogline{{•}} '''TL:'''&nbsp;Teeline{{•}} '''BL:'''&nbsp;Backline{{•}} '''HA:'''&nbsp;Hackline with Hacks{{•}} '''FGZ:'''&nbsp;Free Guard Zone</div>}}