Drawing with an eraser

It is said that 'Life is the art of drawing without an eraser' but in the current sessions we are looking how 
an eraser, rather than deleting mistakes we make,  can be used to bring highlights to our work. 

Here is a selection of drawings where the eraser is as important in its execution at the pencil

 In this drawing of a glass it would be easier to shade the whole of the interior of the glass with its shadows, dark lights and reflections and then pull the straw out using an eraser afterwards than to try to shade around the straw.