Protective wrap on frame

This is my first post here, as I'm just a beginning mt. bike racer (28 years of running and x-c ski racing though). I finished my second Cheq 40 race this past weekend. At the start line I was looking around at bikes/equipment/etc. and noticed that a large percent of bikes had protective wrap around the frame just below the chain. Looked to be about a foot long, made of black rubber or foam material and taped tight around the portion of frame that extends to rear axle - my description shows how much I know about bike terminology. Anyhow, what is the purpose of this wrap? Thanks.

You are describing a homemade chainstay protector, but they are also available from any bike shop. It protects the chainstay (tube from bottom bracket to rear axle) from chainslap (the chain repeatedly slapping the chainstay). Repeated chainslap will quickly chip off the paint, and slowly chip away at the frame material itself.

Thanks, figured it had to be something like that.

Rather than homemade, try searching for 'lizard skin' brands at the bike web sites or dealers. They're great looking and good protection.