The present invention is an anchoring device for joining three boards. It includes a substantially flat horizontal top element having a top view configuration which includes two sides and has a first predetermined width as measured wide to side at its maximum width between the two sides. There is at least one substantially vertical support member attached to the underside of the top element along an imaginary center line and extending downwardly from the top element for a predetermined length, which has two sides and a second predetermined width as measured at its maximum width. There is a substantially flat horizontal bottom element with two sides and has a third predetermined width at its maximum width. The first predetermined width is greater than the second predetermined width and the third predetermined width, and the third is greater than the second.