I admit it does sound a bit iffy but its basically an oak chair leg jammed in your fermenter. Raj was on one of the Basic Brewing Podcasts and is a sour beer fan to say the least.
Here's a link to his in-depth study of sour brews:
http://www2.parc.com/emdl/members/apte/GingerBeer.pdfAnother guy modified the idea and it looks pretty cool:
http://madfermentationist.blogspot.com/2007/02/8-homebrew-barrel.htmlThe idea is that the Roeselare bugs make themselves at home in your flanders brew, work down the sugars, and turn the batch sour. They need some oxygen and a temporary home so you attach a toasted oak taper and go to town. Funky stuff.