Ok folks, I have done some reading and searching on this topic but I am still unclear.    I make a knife sheaths and have made some holsters of the years.   I used veg tan for that.  Mainly so I can tool or carve.  I have also read over the years that chrome tan is a no go with anything metal ie guns, knife blades etc. In regards to sheaths I have made I recommend folks kep thoer knives stored outside the sheath since the leather can hold moisture.  That being said I am guilty of not doing that