Some assembly operations require varying degrees of tightness for a successful assembly.


How to describe visually the amount of tightening required for fixings.


  • Some assembly operations require fixing using threaded fasteners such as nuts and bolts or screws.
  • In some cases these need to be fastened tightly, in other cases the fixing needs to be left loose for product function or to allow subsequent assembly steps before later tightening.
  • Images cannot show spatially the very small differences in arrangement and distance associated with different degrees of tightness.
  • When shown an assembly operation using threaded components users will typically assume the operation calls for a tight fastening of components.


When showing an assembly operation using a threaded component a pictogram should be used, indicating the degree of tightness required for the operation.

Note: This is a learnt convention and thus should be supported with text if possible to ensure comprehension. Alternatively it may require modification of the design of the product to eliminate the need for loose assemblies.

This can also be addressed using the Do This, Not This pattern showing the favorable assembly mode compared to the unfavorable assembly mode.


Drawn from practice and inspection of existing artifacts.

Related Patterns:

Child to:

Discernable Detail

The need for discernable detail may require enlargements of some areas so parts can be identified.

See Everything

The need for the entire object to be depicted to provide contextual information may result in smaller details being difficult to depict and discern.

Return to Zones


Author - Four Legged Stool PAIs used as part of the thesis.

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