The last post tells the truth about modern practice.The days of using a board and pencil or even using a computer as a 2D drawing system have faded away.A 3D model will help you avoid spatial clashes and can be viewed from any angle and with layers turned off or objects hidden for clarity you will have no trouble visualising the article.Best of all you can now find 3D CAD systems for little or no cost and why wouldn't you?Should you need a 2D drawing for any purpose a couple of mouse clicks will get you there.