The RECTANGLE tool is located in the upper left of the toolbar.
The CORNER RECTANGLE tool defines the corner points of a rectangle along the diagonal as well as the length of each side.
The CENTER POINT RECTANGLE tool defines the Center of the rectangle (Where Diagonals Cross) as well as the length of each side.
Which to use comes with experience:
All lines should be black when they are fully constrained
On the sketch created in MyFirstPart:
CREATING A CENTER POINT RECTANGLE
CREATING A CENTER POINT SQUARE USING THE OPTION KEY
CREATING A CENTER POINT SQUARE USING THE OPTION KEY
CREATING A CENTER POINT SQUARE USING THE EQUAL SIDES CONSTRAINT
CREATING A CORNER RECTANGLE
Note: you can use the same methods described in the center rectangle to create a square.
LEFT CLICK on the lines of the rectangle to delete and press DELETE on the Keyboard or RIGHT CLICK on a yellow line and select DELETE SKETCH ENTITIES.