To Select the Midpoint of an Element (with AccuSnap)

Select MidPoint Snap mode.
Move the pointer over the required element.
AccuSnap displays the element's midpoint location.
If necessary, using the tentative hint as a guide, move the pointer toward the required snap point until the tentative snap point marker displays.
Enter a data point to accept the tentative snap point.

Selecting the Midpoint of an Element using Midpoint Snap Mode