Centering an object on top of another

Hi all… I’m working towards making a dovetail on an object and in this case I’m trying to center a smaller rectangle perpendiculaR to another larger rectangle. But I don’t know how to accomplish this… thoughts?

Hi, after you have drawn the large rectangle, the centre point is indicated and you can use this as a reference point when drawing the smaller perpendicular rectangle.

Draw a line accross the centre
Draw lines parrelel lines for smaller rectangle 1mm away from the centre line on both sides
Then delete the centre line and you will have a well centred pendicular rectangle with equal spaces at both sides

Alternatively make it easy on yourself by Sketching the two Rectangles as shown square onto the Grid set, in this case, to 0.5mm.
Make a Copy and Rotate to the Desired Angle and move it to the position required: