Alternatives to blue tack, for large posters/pics etc?

[Pannacotta]

Have tried using Blue Tack but the posters keep falling off the wall!
Are there any decent alternatives out there?
TIA

Poster hangers which are plastic grippers which you slide the poster into. One of them has string attached to hang it up on hook/nail.

These are they

Thanks MrsS, I forgot about those, we used them when I was a child (all those many moons ago!!!).

Yep, a student flat memory for me!