Mark & Anna Enenbach family - circa 1935

Back: Mark, Phyllas, Henry, Perdita, William
Front: Vivian, Mark, Anna, Eileen
When the triangular part of the flap is placed first over the picture and under the larger flap, you get this triangle design at the bottom which damages the picture.
Fortunately I can repair this in most cases but it takes a lot of extra time.

So if you have those old pictures with a bi-fold cover, make sure to fold the larger flap first so it covers the picture completely and then fold the triangular flap last.