(after stating the facts as above). In Friestedt v. National Interlocking Steel Sheeting Company, 195 Fed. 757, herewith decided, we reviewed briefly the piling art and referred to the more extended exposition thereof in the Circuit Court’s opinion reported in 182 Fed. 836. Our study of the prior art convinces us that the principal patentable novelty (if any) of the Simon structure lay in the “hollow beam” as the interlocking means by which two I or channel beams could be united into piling. If invention was also exercised in choosing the I and channel beams of commerce as the material for the sheet members, the result would-be the same as if the “hollow beam” were the only novel feature, because each claim of the patent makes the “hollow beam” an indispensable element. So infringement can be found only in those pilings which use a hollow beam, substantially like that described in the patent, as the means for interlocking the sheet members.
Appellees’ piling is made under Friestedt’s patent No. 707,837, considered in the other case. Its interlocking means is a slot, formed by bolting a Z-beam upon the web of a channel beam near its flange, into which the flange of a second channel beam may be slidden and be held. This is essentially the old and common interlocking tongue and groove. Such a construction cannot properly in our judgment be held the substantial equivalent of the “hollow beam” of the patent.
The decree is affirmed.