I recall seeing in either MR or RMC an article (from the 1960's) covering all types of dual gauge switches and draws. There were some 20 different styles depending if both were dual gauge or some were SG only or NG only and which side the common rail was.
If I recall correctly, the was a photo of a draw that was accomplished without gaurd rails - it used switch points and had to be thrown each time a train of a different gauge wanted to use it.
I've not been able to find the article - I'll keep an eye open for it.
Doug
P.S. a draw is also used on a balloon loop.