Thanks for your answer and also going to the trouble to take a picture. Someday I hope to have some of those PVC dispensers.Don't put it in their feed, too much calcium is bad for their kidneys. Just offer it free choice. What I did was bought an 8 ft piece of PVC pipe 2 inch inside diameter (I think is what it is) and two 90 degree elbows, two end caps and a roll of ducting hanger tape stuff. I cut one piece 1 foot long and the other 20 inches the 1 foot piece I used a Dremel tool and cut a rectangular hole in it and rounded and sanded the edges. Then just put them together in the L shape they work fine. I have them in the coop one has grit and one has oyster and egg shells.
Went out and took a pic please excuse their mess.