Dayton Superior 123707 3" x 3" x 3" CWD Series Wire Dobies Block with Tie. Dayton Superior Combination Dobie, Series: CWD is used for supporting wire mesh or rebar to ensure proper placement during construction. It has a standard strength of 4000 PSI or a heavy duty strength of 5,000 PSI. The CWD com es in mutlple heights within a single unit. CRSI Class 1, D.O.T Approved. Supports rebar m ats and wire mesh to provide proper concrete cover of rebar that is used primarily in horizontal rebar applications.