If you ever see a manhole cover with square pegs, then you can certain that that manhole cover is quite old. The squares were needed to provide a grip for horses and have since lost their main purpose.

Manhole covers are sometimes stolen and this is regarded as a childish prank or simple vandalism. I however feel this opinion is incorrect. My father actually almost fell down an open manhole in China. It was was at night and the area wasn't properly lit. He only hurt his leg quite bad and has since made a full recovery. This isn't something you can describe as a "childish prank" as it can be seriously deadly under the right or wrong circ.u.mstances. It also costs quite a bit to replace a manhole cover. Stealing and selling a manhole cover as sc.r.a.p metal would earn you less than $15 but replacing a manhole cover would cost around $500.