Do I need edging around my interlock, or, what is that black plastic stuff around my patio?

It’s called SnapEdge, and yes, you need it.

Interlock patios are made up of interlocking blocks. They look nice when they all fit in snug, with neat, regular joints in between them.

They do not look nice when they start to shift up and down, side to side, left and right, and in out out.

Interlock is called interlock because the friction and weight of the blocks locks them together in such a way that they don’t move.

Now we get technical… (Oh boooy….)

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There are three types of interlock: Vertical, rotational, and horizontal.

Vertical interlock is achieved by the sides of the blocks gripping together and not letting the blocks pop up or slip down.

Rotational interlock is achieved by having a lot of blocks squished all together, preventing the interlock from rotating, because if you tried to rotate a block, the rectangular structure of the block would cause it to push the other blocks away.

So we squeeze the blocks in tightly and they keep each other in check.

The pattern helps us achieve horizontal interlock, so the blocks don’t move around on their bellies. Having a nice solid pattern means that the block can’t push an other block around without pushing all the blocks.

Now you may be sensing a theme here.

I am definitely sensing one.

If you want these interlock methods to work, you need them to be tight!

You need them to be cuddling close!

But if the interlock is allowed to creep outwards, the patio blocks won’t be tight.

So we need something to keep those sneaky creepy patio blocks from creeping.

We need SnapEdge.

And that is what that black stuff is called. And that is why you need it.