Trail "Blazes" ...

Could someone help me out regarding those various colored trail direction markers/blazes/squares/diamonds that I see at the trails like Sals, Jacobsburg, and Bear Creek (plus others). I read in another thread about Sals getting some new ones and was wondering where you all are getting these from. I have made some in the past from some donated material but don't have that source anymore. I need to replace and put some new ones up here in my neck of the woods and would appreciate some leads. Also, any suggestions about appropriate size (as to see them well but not be obnoxious), preferred height, and fastening (aluminum nails?). Any and all info would be great. I don't remember a thread or discussion regarding this in the past. Much thanks !

BW