I would go as far to say something like this in the body of the claim: "a member sized to fit within a door or window frame..." or whatever else ties a structural characteristic of the device to its use.
Anybody see a difference in scope between
A device for marking the position of a hinge on a door frame, the device comprising:
a member sized to fit within the door frame...
A device comprising:
a member sized to fit within a door frame
Does either one require the infringing device to include the door frame?
I see a potential difference, and my thinking is tangentially related to a parallel thread concerning the limiting effect vel non
of recitation in a preamble. In option 1 "a door frame" may only serve to clarify or give context to what is meant by "sized" (sized how? for what? for a door frame of course). The later recitation of "the
door frame" suggests to me that it refers back to its antecedent a
door frame, and that the drafter therefore intendend that the door frame is a structural element of the claim (I have an "a" followed by a "the")
In option 2, there is no prior recitation of "a door frame", so it modifies or limits or clarifies what is meant by "sized", or is an attempt to do so.
IMO, whether "sized to fit within a door frame" is indefinite depends on what is in the spec and what PHOSITA understands as a door frame. But I think that, standing alone, it is a risky limitation unless augmented with functional limitations. Understood, functional limitations at the point of novelty are subject to attack. But here they would serve a different purpose - clarify what it means to "fit within a door frame"