What is Deferred Perpendicular and Deferred Tangent?

Sometimes when Object Snap is on, we may see the Deferred Perpendicular tooltip.

We all know Perpendicular in the Object Snap mode, but what does Deferred mean and what’s the difference between Deferred Perpendicular and Perpendicular.

When in Perpendicular snap mode, we usually specify first point and then snap perpendicular. Deferred perpendicular is the opposite, we need to specify the line then the point.

We normally do not see the Deferred Perpendicular, because some commonly used snapping mode such as endpoint, midpoint or intersection and some users may turn on all the snapping mode options, making the Deferred Perpendicular rarely seen.

Deferred Perpendicular snap mode work like this:

1. Draw a line as baseline, and then execute Line command,
2. When prompted to specify first point, click Deferred Perpendicular or enter Per.

3. Leave the cursor on existing line, the tooltip then reads Deferred Perpendicular, the symbol is also different from regular Perpendicular symbol, shown as below,

4. We can choose a random point to specify snapping of deferred perpendicular, and then move the cursor away from the line, we can see that a line vertical to the existing line is move along with the cursor, shown as below,

5. Then click to confirm the endpoint of the line to complete.

Beside Deferred Perpendicular, there is Deferred Tangent that works in a similar way.

Select circle or arc when in Tangent snap mode, then move the cursor to specify the endpoint, we can see the line moves along with the circle or arc, shown as below,