These menu items switch you between the following design modes:
Concept - design a structure
Beam - design a beam
Column - design a column
Note that switching modes does not close the mode you are leaving. It will remain open until you select Close from the File menu.
The Mode button in the Tool Bar acts as a shortcut for the entire mode menu. If a member is selected in concept mode, Sizer will go to the appropriate mode; otherwise the program will cycle from Concept to Beam to Column if the mode button is pressed.
Note that beam and column members from Concept mode can be transferred to the other modes for a more in-depth study. Simply click on the member in Concept mode and then click the Tool Bar Mode button or use this menu to select the destination mode.