To Create a Dimension
1. Click Insert > Dimension.
2. Click New References or Common Reference. The ATTACH TYPE menu appears.
3. Pick entities to be dimensioned.
4. Middleclick to locate the dimension.
5. To indicate endpoints of the dimension, select one of the following from the ATTACH TYPE menu:
◦ On Entity—Attaches the dimension to the entity at the pick point, according to the rules for creating regular dimensions.
◦ Midpoint—Attaches the dimension to the midpoint of the selected entity.
◦ Center—Attaches the dimension to the center of a circular edge.
◦ Intersect—Attaches the dimension to the closest intersection point of two selected entities.
◦ Make Line—Creates a line for the dimension to reference.

You can change the attachment type while making a dimension. For example, select one point using Midpoint and select On Entity and make the second pick.

When there is more than one way to create a dimension, the DIM ORIENT menu displays the following to define the orientation:
◦ Horizontal—Measures the horizontal distance between the points.
◦ Vertical—Measures the vertical distance between points.
◦ Slanted—Measures the shortest distance between points.
◦ Parallel—Creates a dimension parallel to a reference line.
◦ Normal—Creates a dimension normal to a reference line.
When dimensioning between two arcs or an arc and a line, to place a dimension you must select one of the following from the ARC PNT TYPE menu:
◦ Center—Measures to the center of an arc.
◦ Tangent—Measures to an imaginary tangent drawn at the point you have picked on the arc.