Frame Rule (City Rule)

The City Frame & Lens Rule (sometimes known as the Serelo Rule) was designed at the City University, London. This rule can measure the following aspects of frame and lens parameters: 

Angle of crest.  Angle of let-back.  Angle of sides.  Downward angle of drop.  Frontal angle of pad.  Inward angle of drop.  Splay angle of pad.  Vertical angle of pad. 

Apical radius.  Boxed lens size and centres.  Bridge width, crest and height.  Distance between centres.  Distance between lenses.

Distance between pad centres and lenses.  Distance between pad centres and tops.  Distance between rims.  Frame head width.  Frame temple width.  Front to bend.

Frontal width.  Height of pad centres and tops.  Inset of pad centre.  Joint height.  Joint size.  Length of drop.  Length to bend.  Length to tangent.

Projection of bridge.  Lens insets, progression heights and segment positions.  Segment diameters height and size.    

Supplied with an illustrated manual.