Duplicate Tool

When you are making a model and you finally get one side of it complete and you want to make the other side the exact same way, a lot of people spend a whole lot of time just try to look back and forth trying to make the other side the exact same way. There is an easier way to do this though. You don't have to remake the whole other side or try to copy and paste. Just duplicate it and when you're editing one part on one side it automatically does it to the other side. Here's how you do it:

1) First you get your model. Mine is half a man. I have the arms, the legs, the head and the torso. 

2) Next, by hitting Alt and left clicking on your mouse, rotate your model so you can see the inner faces of your model. Then right click on your mouse and drag it over the Face option and then release. This will allow you to select different face on your model.

3) Then select all the inner faces. You can do this by holding down the Shift key and clicking on all the faces as shown in the image bellow.

4)Now you have it hallowed out and you can see the inside of your model.

5) Now right click again but this time drag your mouse over the Object Mode option and release. This will allow you to select the whole model.

6) After selecting your model, go to Edit and click on the box next to the Duplicate Special option. It is very important that you check the box and not just hit the option by it's self. You'll understand why in the next step.

7)The reason why it's important to check the box next to the Duplicate Special option is so this option box will pop up. Next to where it says Scale, in the first box, make sure it says -1 and not just one. This will allow it to mirror the first side of the model instead of just copying it. Also at the top make sure you click on where it says instance. Then hit apply.

8) This is what you should see now it duplicated and mirrored the first half but not the way we need it to be.

9) Select the second half and click on the move tool on the left tool bar and use the yellow arrow to position it in the right place to where it looks like an actual man.

10) Now you canmake any changes to any side and it will automatically do it to the other side. If you look in the image bellow you can see that I hovered my mouse over a part of the model on one side and it highlighted that same spot on the other side. Your model will always be symmetrical.

Now you have your 3D man =)