Locate the functional contact
Identify the features that locate, support, retain, seal, or otherwise interact with another part. Explain the intended function of each important contact. A nominal dimension describes a target geometry, but the assembly also depends on acceptable variation and the behavior expected in use.
Mark which surfaces are functional and which are mainly visual. That distinction helps focus a review on the dimensions and conditions that affect the assembly. It also reduces the temptation to apply the same level of control to every feature without a reason.
Separate nominal geometry from acceptable variation
A digital model can show parts that meet exactly at their nominal dimensions. A physical assembly involves variation from manufacturing, finishing, and inspection. Tolerances communicate permitted dimensional variation; their selection should follow the function and a feasible production route.
Consider interacting features together. A gap or engagement may depend on several dimensions, not just the tolerance on one part. A qualified review may need an appropriate tolerance analysis rather than an assumption that individually acceptable parts will always produce the intended result.
Include material and process assumptions
A change in material can lead to a change in manufacturing method, achievable geometry, finishing, or dimensional behavior under the intended conditions. Describe those dependencies explicitly. Do not assume that a new material can inherit every requirement of an earlier prototype unchanged.
Temperature, moisture exposure, loading, and time may matter to the particular assembly. The relevant effects and their significance need application-specific evidence. The useful question is not simply whether a material is stable, but which dimensions or interfaces must remain within which agreed limits under which conditions.
Use fit samples for a stated purpose
A prototype can reveal access difficulties, interference, or an unclear assembly sequence. Record what its material and process allow the observation to establish. A sample made for visual review may be useful for discussing layout while offering limited evidence about the behavior of the production interface.
Keep the prototype's revision and the mating-part revision together. If either changes, decide whether the previous fit observation still applies. Avoid carrying a successful early assembly forward as an unqualified approval of a later design.
Transfer the interface questions
A handover can include a functional-contact sketch, critical-dimension references, material and finish assumptions, observation notes, and unresolved verification actions. Identify who approves a dimension, a substitution, or an acceptance method.
This guide is an introduction to organizing interface questions. It does not supply a tolerance value, a material approval, or a substitute for qualified engineering analysis. Use the actual geometry, process capability, and operating context to define the necessary review.