Chapter 9 Profile Tolerances 323 An alternate option when a unilateral profile tolerance is required is to draw a short phantom line parallel to the true profile on the side of the intended unilateral tolerance. A dimension line with arrowhead is placed on the far side and a leader line connects the feature control frame on the other side, as shown in Example 9-8. The Drawing The Meaning Unilateral Profile Tolerance Unilateral Profile Tolerance The Drawing The Meaning True profile True profile 0.4 profile tolerance zone 0.4 profile tolerance zone Example 9-8. An alternate method for specifying a unilateral profi le tolerance uses a phantom line to indicate how the intended profi le tolerance applies to true profi le. Profile of a Surface A profile of a surface tolerance is used where it is desired to control the entire surface as a single feature. The profile of a surface geometric characteristic and associated feature control frame are detailed in Example 9-9. Profile of a surface is a blanket tolerance that is three-dimensional and extends along the total length and width or circumference of the object or feature(s). In most cases, the profile of a surface tolerance requires reference to datums for proper orientation of the profile. Symbol Specifications H = Letter height H H 2H 2H Example 9-9. A feature control frame with the profi le of a surface geometric characteristic symbol and datum reference.