1. Open Autodesk Inventor (Tech & Engineering-->Tech-->Autodesk Inventor). It will take a minute or two to load. Once you see the welcome screen, select "NEW", and then choose a Standard.ipt template, depending on if you want to use millimeters or inches to measure everything. "IPT" stands for "Inventor Part".

2. Click "Create 2D Sketch" and select a sketch plane to put the sketch on. Think of sketch planes as pieces of paper--you first draw something on it, then you use the modeling tools to the flat, 2D sketch into something 3 instead!

3. Now you should be in sketching mode. You'll different tools on the toolbar--line, circle, rectangle, arc, etc. Choose a tool and draw a simple, closed loop shape (no breaks in the line--must be connected). Avoid intersecting lines, and if you DO have intersecting lines, use the Trim tool to remove them. As you sketch a shape, you can also type in measurements (dimensions) as you go. You'll want to get in the habit of using real-world dimensions in your sketches.

Once your sketch in complete, click the green check mark, "finish sketch".

4. Back in 3D modeling mode, click the Extrude tool. The first time you use a 3D tool, the options box will be collapsed--click the little black triangle to expand for more options. You can type in the depth you want to extrude the object.

Extrude as a Cutting Tool

5. Next we'll sketch another shape on our box and then use extrude to cut it out. You can sketch on ANY surface that is FLAT. Click Create 2D Sketch and choose a surface to sketch on. Click on it!

6. Sketch your shape--must be a closed loop again--and then Finish Sketch. This time, I've used the circle tool. Whenever you place a circle, you must click where you want its CENTER POINT to be. So click to place the circle, then move your mouse out to expand it from the center point. Click again to create the circle. You can also type in a specific diameter for your circle before you click a 2nd time.

7. This image demonstrates the use of the equal constraint and the trimming tool. With the equal constraint selected, you can click on two things and they will become equal in size--I used it on the two smaller circles (the "ears"). The trimming tool can be use to trim intersecting lines, which cause problems for extrude. Just click on the lines you want to eliminate.

8. Once you're back in 3D modeling mode, click on Extrude again. This time, we're going to select "cut". Then just click on the shape you want to cut out, type in the depth of the cut, and click ok.