WTF is living under my step? Do I need to move out and burn the house down?

[OutOfSyncWithReality]

Ok, I'll try and explain what I mean by step first - when I got patio doors put in my lounge they put a piece of wood in between the door and the floor, it sits just above the carpet by about 0.5cm. I don't know how else to describe it but I have attached a photo. I hope that helps.
Anyway, on to my point. There is a sort of cobweb on the step's lip. I can just about see what I can only describe as 1 inch long black antennae. My first thought was spider legs but I can't see a joint (knee? do spiders have knees?) - unless they are so bloody long that the joint is under the step which I can't even begin to think about. What is this? Do I have a new pet? Do I have to burn the house down? Help!

There is absolutely nothing there in the picture.

Can’t see a damn thing. Maybe a house elf?

Looks like slightly frayed carpet to me. Definitely not a spider or similar. (I live with a lot of spiders).

It's one of those tube web spiders that sits with feet hanging out can you see web trip wires?

I can't see anything?

I can't see much, either. Spiders almost always jump back into cover, if they feel anyone/thing coming.

The step is called the threshold, mine is painted white. On mine the edge of is rounded, underneath it, roughly 2cm in, it has what looks like piece of wood along the length of it, the carpet butts up to this. Not sure if it’s a slat of wood glued on or the threshold is preformed MDF in one piece.
Spiders are everywhere, some are massive. We have one living in the garage with legs so long they stuck out from under the rim of a pint glass when I trapped it one day, I let it go outside and it scuttled back in and hid behind the fire extinguisher. no way am I moving that extinguisher to find it.

Frayed carpet? Can you poke it with something and see if it moves?

I think OP put the pic to show us what she meant by ‘step’, not to show us what actually lives under there.

I’d bug spray the sh*t out of it OP. Whatever is under it would probably come out then to breathe.

Get the hose out and clean it all away.
We have a similar problem, above our front door is an extension to the garage roof so between our garage and front door there's a covered walkway to our front door. We have a spider in a hole, my kids were scared so they called it flapjack and all seemed less scary ... until flapjack had billions of babies and got a lot bigger ... but our hose doesn't reach 😨 so she still lives there 😱

Hoover it

Noooo! Coax it out with pan pipes and re-home it in an old building somewhere. I'd do it for you but I fear we are not neighbours.

I think OP put the pic to show us what she meant by ‘step’, not to show us what actually lives under there.
Thank you Rosiiee, yes just to show the step, not what is living under it. I only noticed while I was wearing my glasses, you can’t actually see it with the naked eye. DP is coming over later. I’ll get him to give it a prod.