Component Type for project idea

I’m making a project which involves a rod which can slide freely in and out of a tube. However, on the edge of the tube, I’d like a device that can grasp onto or brake the rod and stop it from moving. The device would be controlled by an Arduino which is communicating with a PC. The device would only have to be able to prod downwards and hold and thereafter at some point retract. If applying pressure is an issue it could otherwise be something that prods into premade crevices of some sort along the rod. I’ve attached a diagram of what I had in mind. My question is simply what kind of components I could use to make it.

Braking Device.PNG

Maybe a solenoid with an attachment like rubber.

Like this: https://www.sparkfun.com/products/11015

PhilBer: I'd like a device that can grasp onto or brake the rod and stop it from moving.

Solenoid, rotary solenoid, servo, motorised cam, electromagnet...

What's it's going to be made of and how much force do you want to apply?

Yours, TonyWilk