this thing cuts through trees like butter, ive found a few sled magnets in the last couple of years... 
http://www.amazon.com/Gerber-Exchange-Blade-Utility-Serrated/dp/B000BYDFWK/ref=pd_bbs_sr_3?ie=UTF8&s=sporting-goods&qid=1227131246&sr=8-3
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http://www.amazon.com/Gerber-Exchange-Blade-Utility-Serrated/dp/B000BYDFWK/ref=pd_bbs_sr_3?ie=UTF8&s=sporting-goods&qid=1227131246&sr=8-3