 Interpreting engineering drawings, geometric dimensioning and tolerancing, the feature control frame. Many older drawings controlled geometric tolerances by displaying a note such as all surfaces parallel and perpendicular to each other within .001. Today the method used to specify geometric tolerances is a feature control frame. A feature control frame consists of a rectangular frame that is divided into two or more compartments. The first compartment of the feature control frame contains a geometric characteristic symbol. Straightness, profile of a line, parallelism, circular runout, cylindricity, perpendicularity, symmetry, circularity, angularity, concentricity, flatness, profile of a surface, position, total runout. The second compartment of the feature control frame contains the tolerance, five thousandths of an inch. Where applicable the tolerance may be preceded by the diameter symbol. The tolerance may be followed by a material condition symbol, at maximum material condition, at least material condition. The tolerance may also be followed by a datum reference letter. Multiple datum primary references may be listed after the tolerance. This is an example of a primary datum. This is an example of a secondary datum. This is an example of a tertiary datum. A datum feature symbol is used to establish and designate a datum feature, as shown below. When a feature that is controlled by a geometric tolerance is also the datum feature, the datum feature symbol may be placed on the feature control frame. When a circle is placed at the intersection of the leader elbow, it means that the profile tolerance is applied to all surfaces. This all around symbol is also used in welding drawings to indicate that a weld is placed all around an area. You have completed this activity, interpreting engineering drawings, geometric dimensioning and tolerancing feature control frame.