I love mine. You use the cake boards same as you normally would.
You can buy them in different heights. So what I do is I buy the 4 inch ones and I bake my layers and level them to 1 1/2 inches add my filling at 1 inch and by time yo have 2 layers of cake and 1 of filling it's 4 inches tall. I stand the cake jack next to my cake and screw it up to thew height of my cake. Then insert them into your cake just like any other supports.
You can screw them up or down depending on your needs for height.
I do tell people they are there and either figure in the cost into my prices or I charge a fee for returning them = to the amount of replacing them+shipping if you get them that way.
They wash up beautifully, by hand though.<<<<<

I use them for my stacked cakes all the time.