STL part file and renderings can be accessed here Brass knuckles
Download this image.
Open solidworks, choose part and click OK:
Click on Sketch and choose any plane to sketch on.
Choose Sketch Picture and open the picture you downloaded.
Carefully using Sketch tools follow the contours (there is Autotrace add-in in Solidworks, but i would not recommend using it for better end result)
In the Features tab, click on Extruded Boss/Base.
Choose the thickness you prefer. 30 to 40 mm seems okay. Click on the green tick.
To make our part more appealing we are going to add fillets.
Click on the left button and drag the mouse over the part to select all the edges. Choose the radius you like. In my case, i chose 3mm. Click the green tick and you are done!
Do not forget to hit "It worked" if you liked the tutorial.