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       << Click to Display Table of Contents >> Navigation: MechDesigner Reference & User Interface > 2.2 Mechanism-Editor > MD-Solids > Add / Update Polyline | 
    
A Polyline sketch-element is a sketch-loop* that is a copy of the shape of a 2D-Cam and Gear-Pair.
You can add Profile/Extrusions to a sketch-loop.
Therefore, you can model 2D-Cams and Gear-Pairs as MD-Solids.
* If a 2D-Cam is “Open”, or the gears in a Gear-Pair are “Gear-Segments”, you must edit the Parts after you add a Polyline to add sketch-elements to close the sketch-loop.
STEP 1: Put the MMA to Zero degrees 
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STEP 2:Start the Add Polyline command: 
 The Command-Manager has one selection-box.  | 
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![]() Command-Manager  | 
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STEP 3:Select a 2D-Cam or Gear-Pair To add a Polyline to a 2D-Cam or Gear-Pair: 
 OR ... To Update the shape of the Polyline to the new shape of a 2D-Cam or Gear-Pair: 
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The 2D-Cam or Gear-Pair is in the Command-Manager selection-box. ![]() 2D-Cam element in the Selection-Box  | 
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STEP 4: Complete the command 
 The Polyline is now a sketch-element in the Part that is the shape of the 2D-Cam or Gear-Pair.  |