I am not actually to be honest.
In the grandscope of things those bits of string attaching a breeze block are utterly pointless.
It only gives an addition 1 knt of wind difference to not having 3 bricks attached. 3 concrete filled tyres at 50-70kg each gives an additional 4 knts.
And if the concrete is sliding along tarmac there won't be that much friction to be honest.
Basically if you can move it by yourself without requiring a forklift its useless as a tie down.