Cinder blocks & several wood posts (Berkley)

Does anybody have some cinder blocks and/or 4x4 wooden posts they would like to part with?
I live in a rental property & desperately need to build a makeshift fence that's movable but sturdy and respectable, that doesn't look trashy.
Why? Well, to keep my neighbors 3 kids OUT of my yard for the rest of however long they'll be staying here (technically they've been evicted but for some reason it's taking them SO LONG to finally be removed).
They are all horrible people in so many ways but the number 1 reason I urgently need a fence is because recently we discovered that they've tortured & killed *at least* 2 of the feral cats that live around here that we & another neighbor take care of, like TNR'd, fed them, looked out for their well-being, etc. (Yes the police are aware but can't do anything without it being on video or caught in the act basically).
I know that at least one of our poor cats was lured by these rotten children as they were sprawled out across my yard (which is connected to theirs, no fence or anything) with a bowl of food & a bit of determination.
We are devastated by this and would like to do everything we can to prevent this from happening again in the future.
They've always have a real problem following directions and minding boundaries, but only now did we become aware that they are cat murderers so until they are gone we need to do something to prevent our sweet outdoor friends from suffering the same fate. We don't have much money at all, which is why I'm hoping someone on here has some extra materials they are done with or wouldn't mind parting with that we could build a fence with ASAP.
THANK YOU so much in advance.