harlequin pattern

I have started crocheting an afghan that has a "harlequin pattern." I don't know if this is a common pattern or only refers to this particular project. I am unable to understand the instructions, specifically: "sc in ch 1 sp two rows below (how do you do that?), enclosing the ch 7 (3 dc, ch 1, 3 dc) in top of 6 dc-tog". I don't know what they mean by "enclosing". The dc-tog I think I figured out. If anyone can shed light on this, I would appreciate it.