Mine were welded, then cut off and frabricated to be removable. Welding plate remained and the attachment occurs with the tube from the slider sliding over the solid tube on the welded plate. It all attaches with bolts and lock washers. Two attachments for each side. It's sweet because I can remove them when not needed (gets your pants dirty when you get out if you're not careful) and put them on when I take it out for some fun.

Can post pics if anyone is interested...