[Coodeville]

held in place on the seats of my 1970 Cadillac?

[DanTwoLakes]

There are generally two ways they are held in place. Some buttons have an "eye" on the back of them and are held in place with button twine attached on the back of the seat cover with a slip knot.
Other buttons have a threaded or smooth nail that is held in place on the back of the seat cover with a spring steel washer.

Buttons with eyes are the easiest to repair without taking the seat cover off, but with a threaded or smooth nail, you will have to take the seat cover off to remove the spring washer from the button.

[lamx]

Don't know about a 1970 Cadillac specifically, but all the buttons I have seen on car seats are prong type buttons with a metal clip behind the upholstery to hold it on



Button

Ed

[DanTwoLakes]

Except that what you have pictured is called a threaded nail with a spring steel washer. All of the nail type buttons come with any length nails for different thicknesses. The two button backs in the front right are called prong buttons, and the button backs on the left are for eye buttons. The two button backs on the top center are smooth nail no-dent button backs which can also be held with the spring steel washer.