Properties 
Methods 
Rectangle with edges parallel to coordinate axes
The Rectangle object represents a plane rectangle with the sides parallel to the axes of coordinates. It is used in various methods and properties where the object size is needed or should be set.
Use methods RectangleByLimits or ZeroRectangle of the Application object for the new Rectangle object creation. Each of them creates a new rectangle, with specified or zero size respectively. Once the Rectangle object is created, it may be utilized for many tasks.
Left, right, top and bottom boundaries of the rectangle, respectively. All these properties are available for both reading and writing Coordinate axes direction depends on the way of usage of the rectangle. For example, rectangle created using the property Dimensions of the geometric object or collection, supposes that the axis of ordinates is directed vertically up. Rectangle corresponding to a client area of a window (property ClientArea of the Window object) is designed to work in the window coordinate system, where the axis of ordinates is directed down.  
TopLeft and
BottomRight
as Point

Return/set points, related to the upper left and bottom right corners of the rectangle. 
CenterPoint as
Point

Returns the center of the rectangle. 
Degeneration test of the rectangle. The IsEmpty function returns True if the height or width of the rectangle is equal to zero. The IsNull function returns True only in case all coordinates – Right, Left, Top and Bottom are equal to zero.  
Returns the width or height of the rectangle respectively  
Methods
Inflate
and >> Deflate 
Each of these methods receives 4 parameters: Left, Top, Right and Bottom those values (with sign) define the increase (Inflate) or decrease (Deflate) of the corresponding coordinate of the rectangle 
Normalize method 
If necessary – swaps left and right or top and bottom boundaries to assure that the left boundary is located to the left (or coincides) from the right boundary, and the bottom boundary is lower (or coincides) than the top boundary. 
SetEmpty method 
Sets all coordinates of rectangle to zero. 
ContainsPoint and ContainsRectangle methods 
Check whether given Point (given Rectangle) is located within the rectangle. Points on the boundary are considered as internal ones. 
IntersectRect and UnionRect methods 
Calculate the rectangle as an intersection (union) of two rectangles. 
SetLimits Method 
Sets all boundaries on the rectangle at once. 