Clearly a product, first of all, the main effect image of a product, followed by a part of the details? There are also scenarios to use the map? Also reflect the process of your conceptualization.

The main effect of the product? Need to reflect the material characteristics of the product? The perspective should be accurate? The key connecting parts should be drawn clearly or expressed clearly. Don't color just because? Marker just to better express the characteristics of the product only? That is to say, its role is to add the icing on the cake. If you draw well enough? If you draw well enough? I believe it would look good without coloring. Such as:

Detailed drawings? The main thing is to answer some structural questions? About how it folds? How are the two parts connected? These

Using contextual diagrams is? It's a more straightforward way to tell people what the product is used for and how to use it

The conceptualization process is the research that you do beforehand. And your thought process? How do you perfect a product step by step? This can be your product looks more full of weight? A good product? This step is the most important

Of course? Layout is also important? It's best to keep it simple. Especially with the software to do out of the effect of the picture? The image size can not be too small