2'x4' maybe 4" thick ('bout standard for household sidewalks) ....hmmmmm..... Hell, someone has already stated the cure....PICK IT UP....WHIMP! Dig a little hole under it on the short side and pick up one end, walk it along by rocking and twisting from corner to corner....sheeesh. I'm old and useless and I believe I could do that.
Oh, excuse me, you're a DUmmie. You need to call the gummint for help.