powerpig posted a photo:

Here’s the final Star Wars sculpture I did for LEGO in 2015, appropriately titled AT-ST on Endor. As you can guess, the legs shuffle back and forth when you turn the crank. The mechanism in both the AT-AT and the AT-ST models is deceptively simple – the legs are pushed outward and return to position through the magic of gravity.

UPDATE: Guide now available at chrismcveigh.com

Note: In 2017, builder Carl Greatrix tackled the same concept, motorized, at a much larger scale. The walking motion in his model is phenomenal - check out his work in progress at www.flickr.com/photos/bricktrix/