Tape to neaten up the external edge of a wall in my sitting room

Some time ago, I'm sure that I read an article about some 'tape' you could buy that you could stick to an external (90 degree edge corner) on an interior wall (in my sitting room - about 2.5 m tall) to make it look neater? I haven't got the time/money at the moment for this to be done by a plasterer.

I will be lining the wall first and later using wallpaper on top.

Does anybody know what this kind of tape is called and where I can buy it, please? Thank you.