How do you check a frame is in good shape?

I just bought an old CLaud Butler off ebay. I want to check that it's in good shape and roadworthy before I go get it powdercoated. You guys know any simple checks that I can do at home? and maybe some issues with old steel frames that are common that I should look out for?

I did the thing with the string to make sure that the rear dropouts are evenly spaced(they werent initially, but then I used Sheldon Brown's method to sort them out) , and the frame looks fine when you inspect it- everything seems in line etc...

I just don't want to get building and then realise that there's some fatal flaw with the frame...

Thanks guys

could check top of down tube (near head tube) for any slight crease to see if it has been crashed.

drastic example: http://www.parktool.com/images_inc/repair_help/frame10.jpg

could be a good idea to make sure all threads are good.. If your building up using second hand parts from classifeids/ebay it might be worthwhile to get them all together and build the bike up first before sending to the powder coaters, make sure it all fits and rides smooth, then take it apart and spend the time that its on the paint shop polishing all those parts so it looks nice once its back together?

Yeah, sounds like a good plan. Cheers guys

tbh if you can't see anything wrong with it instantly and it rolls nice, chances are it's fine.
good luck with the build and enjoy!

If you can strip the paint from the frame first, or even try and get a look at it in the raw state before it's powder coated (they should sand blast it first) then you should be able to see and defects, dents, pittiing or even bodged repairs.

Good Luck

Some old boy said to me, if you get it shotblasted, rather than sandblasted, the thing'll fail somewhere if there's a problem. It's what he does with all his old frames to determine whether they're roadworthy.