MDIChild property
Available for Window objects.
Read/Write at design time
Specifies whether a Window object is an MDI child (used in MDI applications). It can be one of the following values:
TRUE Window object is an MDI child (there must
be an MDIWindow object in the project).
FALSE Window object is a normal window
(default).
REMARKS: When this property is set to TRUE , the corresponding Window object always appears inside the client
area (MDI client) of the MDIWindow object.