For pretty much anything you might want or need to know about corsets, this is a very informative site , that is easy to use.
Corset Gapping – By Lucy’s Corsets
A very informative video on what the gapping in the back of a corset means. She explains what corsets are better, or more suited, for your body type and how to tighten them without ruining them over time.
How to Lace a Corset – By Orchard Corset
A video tutorial on how to correctly put the lacing into a corset.