This thing needs fixing because it's driving me insane. It's not doing what it should be doing and to me it just looks like a bug.

The whole purpose of Blocker is to block items on lets say conveyor belt until sensor triggers it and it allows items to pass forward, allowing complex assembly to be made without items escaping before they are ready to be weld together.

The thing is, it just doesn't do that. When sensor triggers it with a single block element, Blocker element changes the position of the piston so quickly the item doesn't even have time to move forward and remains blocked even though sensor component has triggered the Blocker.

And because of this I almost always had to resort to improvising with the Pusher element and using it in a different way to prevent already constructed elements from escaping down the conveyor belt. Only time I can use the Blocker is when some huge constructed element is passing the sensor, because it'll give Blocker extended period of time being "open" and the items will pass past it fine.

I think this Blocker wasn't meant to behave like it does, but for some reason no one seemed to complain about it and so it never got changed/fixed.

Blocker, when triggered by a sensor, it should allow a single block sized items to pass.

It takes 1 cycle for the blocker to fully retract and a block moves across a conveyor belt in 1 cycle. By the time the blocker is retracted, the single block has moved off the conveyor and the blocker goes back to blocking. That means there's never a cycle available when the blocker is retracted for something to go past it. It confused me at first too, but it does work consistently with the timing of cycles.

For me, I like to have my blockers detect when the last piece of whatever I'm blocking is in place. It unblocks itself when it is done, in other words. For single blocks that need to be synced, I have them stack up against a wall and then push them sideways when I need them, rather than using blockers.

Grilledfish is right.

It does take a 'cycle' for it to retract. And unless you have a 'something' opposite of it ( other side of the conveyor ) ... its going to push whatever you have on the conveyor around.

I also use the 'pusher' as a blocker more than the 'blocker'.

Best use for the blocker ( it seems ) ... is to hold whatever you are assembling in one place, until it is ready for the next step. I use a sensor placed to detect the last block added to 'whatever', that triggers the blockers retracting. With something ( platform blocks ) placed on the other side of the conveyor.

If you make it to the puzzles with the 'laser' tool ... I vaporize the 'too soon / out of sync' blocks with it.