And these are the steps:
1. Rendering of the shoulder 3D model that we are creating.
2. Cross-section or profile of the shoulder, with dimension to be drawn in 123D
Continue working on the same file as in last Step,
3. On the "Sketch" Marking Menu, select New Sketch pill function.
4. Select XZ plane on the Origin Coordinate or "Front" plane (plane on XZ)
5. Set "View Cube" to the FRONT view.
6. The front plane appears with the Origin is on the lower left corner (red dot).
7. Right click on the mouse, to drag the drawing plane closer. Until the Snap value in the Snap Menu display the amount of 0.5
8. Select "Draw" pill in t he "Sketch" Marking Menu
9. Set the starting point at 5mm and 0mm. Then draw the straight line upward at 10mm long.
10. And draw a perpendicular line to the previous line by draw the end point to the left, and input the amount of 1.5875mm using the keyboard input.
11. Continue to draw the line in upward direction, using the keyboard input to enter 12.7 for the length of line.
12. Drag the endpoint of line in the Y direction (toward the right), and enter the length of the line as 11.2mm.
13. Drag the next endpoint downward, and enter 12.7mm for the length of the line.
14. Drag the next endpoint toward -X direction (to the right), and enter the value of 6.6125 for the length.
15. Drag the next endpoint of the line toward -Y direction (downward) and enter 10 for the length of the line.
16. Then join the next end point to the start point of the profile.
17. We now got the cross-section of the shoulder. Next, we will revolve the profile to create solid model.
18. Before we could "Revolve" the profile, we need to draw the revolving axis first. Select "Repeat.." pill on the "Sketch" Marking Menu.
19. Set the starting point of the line at the position of 11.1125 and 10, by using the keyboard entry.
20. Drag the endpoint of the line upward. And enter the length of the to any amount you preferred.
21. We are done with the shoulder profile. And ready to make a "revolve" the profile to make solid model. It a good time to save the file now.
22. Use "View Cube" to set to "Home" view.
23. Use "Pan" function from "Navigation" Tool Menu to reposition the drawing in the middle of the screen.
24. Use mouse "Scroll" wheel (middle mouse button) to scroll drawing closer.
25. Select "Revolve" pill from "Create" Marking Menu.
26. Select the profile when 123D asks for it, and select the axis of revolution. (Note: We did this command before in creating ear steps.)
27. Click at drop down arrow next to keyboard input box, and Select "Full" function from the list.
28. Right click mouse buttom to bring up Marking Menu. Then click "OK" to commit the command.
29. Here we are, the incomplete shoulder. We are going to do some more editing to complete the shoulder solid model. Save the file!