| A | B |
|---|
| Dimension Line | A thin line that shows where a measurement begins and where it ends. |
| Dimension | Another name for a size description |
| Size Description | Another name for a dimension |
| Extension Line | Thin lines that extend the lines or edges of the views. |
| Finish Mark | Or surface texture symbol, shows that a surface is to be machined (finished) |
| Leader | Thin lines drawn from a note or a dimension to the place where it applies. |
| Aligned Dimensioning | Dimensions are placed in line with the dimension lines. |
| Unidirectional Dimensioning | All dimensions read from the bottom of the sheet no matter where they appear. |
| Size Dimension | Define the basic shapes of an object. |
| Location Dimension | Define the relative positions of the basic shapes of an object. |
| Datum Dimension | Dimensions that locate an exact feature. Location dimensions are given from them. |
| Reference Dimension | Dimensions for informational purposes only. |
| Counterbore | To make a hole deeper and wider |
| Countersink | To drill a cone shape at the end of a hole. |
| Limit Dimension | When absolute accuracy cannot be expected, these dimensions are used. They show the largest and smallest dimensions allowed. |
| Tolerance | Distance allowed away from the exact size before the size is wrong. |
| Geometric Tolerancing | Giving the largest amount of variation in form (both shape & size and location) that a system of interchangeable parts can tolerate. |
| Datum | Points, lines, and surfaces that are assumed to be exact. |
