Returns the value of flag. The object has private field:

private int _flags;

This field can be used for storing various boolean properties (CanSplitHorz, CanSplitVert etc), for example CanSplitHorz property defined as:

public bool CanSplitHorz
{
    get { return GetFlag(c_flgCanSplitVert); }
    set { SetFlag(c_flgCanSplitVert, value); }
}