New to Sheet Metal in Solidworks

Never having read word one in the sheet metal part of Solidworks, I hereby ask the following general, but nonetheless admittedly dumb theoretical question: In the making of a sheet metal part drawing, must it be identified firsthand as a sheet metal intention by prefacing the drawing with "base-flange/tab"? Does this tell Solidworks to get into a sheet metal mode? For example if I have a 3" square extruded to .04" thick, (or a simulated sheet metal part), allready drawn WITHOUT the preface of "base-flange/tab", can i make it into a sheet metal part and add two lines one inch from two edges and bend it up 90 degrees to form a channel? If this is possible, I would appreciate a simple step by step method from one of you many Sheet Metal Gurus. Remember, I have yet to cover the rudiments of this subject yet. Thanking you kindly, Erika

Simple answer - yes.
Better answer, not necessarily recommended.
Ok, a bit of explanation. SW has the capability to create a sheet metal part in a variety of ways. One being to start with a base flange. The advantage of this is that it puts you into a sheet metal mode and SW does a pretty fair job of not letting you model something you can't actually create in the real world.
But, sometimes the geometry of the part really doesn't fit that procedure, such as when you have angled cuts crossing bends. Then it's sometimes better to create the model and then "insert bends." (Catch the reference here?) This takes existing geometry and tries to interpret it as a sheet metal part. If you have not violated a cardinal rule, such as all of it has to be the same thickness, then it usually works pretty well.
Another method of putting in bends is to insert a "sketched bend." This is where you have already made the part be a sheet metal part by one of the methods, and then you put a line on the part and tell it to bend on that line. This is sometimes the best method, but in your case I would suggest an edge flange as it's a more standard bend and has some advantages that sketched bends don't have.
So, here's your simple start, but I really must point you to the online tutorial on sheet metal as it's a very good reference for stepping through some of the various aspects of SW sheet metal.
As always, though, come back with questions.
WT
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In addition to Wayne's Comments You can also start a base flange from a profile that is not closed. For example the 3 lines that would define a sheetmetal channel and use a base flange to extrude them to length. This would require only one step to creating 2 bends. This method can also be used to create rolled sheetmetal parts.
Regards, Corey
Wayne Tiffany wrote:
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In addition to Wayne's answer, checkout http://www.sheetmetaldesign.com /
John Layne www.solidengineering.co.nz