Matrix notation in handwriting I understand that typically matrices are printed in bold to distinguish them from other mathematical entities with the same symbols. However I find it difficult to actually handwrite in bold. With what symbol  is it appropriate to distinguish a matrix from an operator, eigenvalue etc. 
I have read this almost identical question (How to do \mathbf in handwriting?) but it doesn't really answer the problem because in the area of physics I am studying the matrices are always indicated by bold, lower case greeks. 
 A: I learned a convention using under lines.  A vector us usually lower case with a single underline.  A matrix is either capital with a single underline or capital with two underlines.
A: The passage typically matrices are printed in bold is only applicable to certain fields of maths. In linear algebra, for example, the standard notation is just capital latin letter for matrices and lowercase latin letter for vectors (opinions divide whether we should add an arrow above a vector).
If you want to write in bold, you can use the same approach as with "blackboard bold", e.g. $\mathbb A$ (\mathbb A).
Another approach (used in mechanics, for example; especially for tensors) would be to use double underline for matrices: $\underline{\underline{B}}$ (\underline{\underline{B}}).
Finally, an approach not related to maths - use a different pen! You can use fountain pens with a stub nib (a lot of models) or a flexible nib (fewer models, but still a lot), which allow line width variation depending on the angle (first option) or pressure applied (second option).
