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DumOleBob -- I'll second the vote for "Drop In" anchors, they really work well for those temporary applications that require a flush floor after removal. The biggest drawback of the Drop-In anchors is that they need to be spaced 10-diameters apart to carry their full rated load. Standard Drop-In achors for a 1/2-inch bolt need a 5/8 inch hole that is at least 2 3/8 inch deep, and deeper is better strengthwise, but you don't want to drill too deep or you run the risk of cracking the bottom out of the concrete when you try to set the anchor's internal wedge. The Rawl Handbook says that the Rawl Drop-In anchors need to be derated by fifty percent if they are installed closer together than 10 insert-diameters, so a 6 inch x 6 inch square pattern of four 1/2-inch-thread Drop-In anchors should be strictly rated for the same load as two of the same anchors that are 6.25 inches apart. If you go with the Drop-In anchors, I suggest that you drill the holes as close to diameter, location, and straightness as you can and then thoroughly scrub the sides of the holes with a wire "bottle brush" or "toothbrush" to clean as much of the pulverized concrete out of the hole surfaces as possible. I'd also suggest that you spring for the factory-made setting tool (rather than using some random pin punch) and use a hand-drilling hammer to drive the wedge. A properly-installed Drop-In will pull out a chunk of concrete before it slips out of its hole, but I see a lot of these anchors that slip out of their holes because they were improperly expanded or installed in oversized holes. Almost all of the major makers of concrete anchors make Drop-In type anchors -- Rawl, Red-Head, and Hilti come immediately to mind, but there are many others and they are work about the same. I sure as heck wouldn't waste my time going from store to store to look for some particular brand of Drop-In. John
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