Bars

In gymnastics, the bars are made from wood and are held in place by a metal structure.
There are some gymnastic moves which only require one single bar and some which require two - which are known as ''A' Bars' due to the metal structure representing the letter 'A'. 'A' bars consist of a low bar and a high bar with a distance of x in between.

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A basic 'A Bar' routine would consist of a mount - circle up or an upstart (and variations), a back-hip circle, a squat on, jump to catch the high bar, then a long upstart or baby giant, then a dismount of most likely a straddle undershoot. 

Many moves could be added into the routine and many moves can be replace with harder moves. Giants could be performed from a cast to handstand while on the high bar and a very common more advanced dismount would be a back-away. 

A steel bar is often used to practice more advanced moves such as giants and stalders. This is due to the gymnast being locked in place by 'gloves and loops', meaning they cannot fall off the bar while practicing. A steel bar will always be a single bar.

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The loops are pieces of fabric which attach a gymnast to the bar and the gloves are simply cotton 'wooly' gloves used to allow a gymnast's hands to slide around the steel bar. 

Please note - I will be taking my own photos soon - but for now I will be using pictures from Google.

1. http://sport-kid.net/bars-gymnastics.html
2. http://gymnasticplanet.com/shop/media/catalog/product/cache/1/image/700x700/f61d3ad1921ed5cb73ee96aaf7518000/b/a/barloops-large.jpg
3. http://cdn2.bigcommerce.com/n-ww20x/jhhzx5/products/159/images/374/Bar_Loop_Gloves__19964.1405351721.368.368.png?c=2