I use a piece of the hand railing you use on stairs. It has a flat area. Works great!

Great idea, Dottymo. I have a hard cardboard tube that I was trying to figure a use for. I will give yours a try.

Update: I did try the cardboard and it worked okay. It's a bit awkward, so I just went to Lowe's and bought a piece of 8' moulding for less than $6 and I have the muslin. I will make my own set.

strip stick
 

I have used one that I had my hubbie cut for me, maybe 18-20 years ago, when I was wardrobe sewing. It was just a 1/2 round from the lumber yard, used without a covering. It produced nice straight, flat seams. Forgot all about it for quilting, duh.

Strip sticks are awesome!
 

I love mine also Prism . I have 2 strip sticks, one long for rows and one short for blocks. I purchased them at a quilt show. The company listed in the video link are the ones I purchased. Check out the warranty:

Warranty: Return the Strip Stick at any time for any reason and receive a new one of the same size for free.

I just used my long strip stick yesterday to press seams open on rows of a completed quilt top. The seams can be pressed open last and not distort the rows.

I have one and use it to iron seams open, but I don't use it that often because I don't usually iron seams open.

I watched someone use it at a retreat. I was all excited about having DH make this then forgot. Thanks for the reminder. (by the way, I love my tailor’s clapper especially for small blocks with numerous seams)