Clothesline Math has been around for quite some time in various forms. I've seen people use ribbons, calculator paper rolls, and of course clotheslines. This manipulative can be great for building number sense and for offering an opportunity for practicing concepts.
The idea is to start with an empty length of rope. Have a few reference point cards (maybe -2, -1, 0, 1, 2) and then the remaining cards would contain the problems to be solved. It could be something as simple as unreduced fractions for elementary school, algebraic expressions for middle school, or even logarithmic expressions for high school.
You could approach the activity in two ways. First, if you have a small class, you could give every student one card and they could place it on the number line in the appropriate place. This gets a little chaotic if you have a large class. Alternatively, you could split your class into groups and have each group complete a task with maybe 2-4 cards to be placed on the number line.
Chris Shore has written extensively about Clothesline Math and has even created a separate site dedicated to the idea. And both Cindy Whitehead and Andrew Stadel have created Desmos clothesline activities.
Here are a few for you to try.
Grade 1: Three addends with groups of 10
Grade 6: Divide fractions by an integer
Algebra 1: Evaluate expressions - These come from Chris's site.
I hope you get chance to try this activity in your classroom. I'd love to hear about how it goes.