In the following illustration, the hole in the holding plate was centered in the rectangle by extracting the X,Y coordinate values from the midpoints of the plate's horizontal and vertical line segments.
The following procedure shows how to use coordinate filters to create the hole. You use a Midpoint object snap to find the midpoint of the horizontal and vertical lines.
Command: Enter circle
3P/2P/TTR/<Center point>: Enter .x
of Enter mid
of Select the horizontal line on the lower edge of the holding plate
of (need YZ): Enter mid
of Select the vertical line on the left side of the holding plate
of Diameter/<Radius> Specify the radius of the hole