Skulch is junk mail

A colloquialism!

In some parts of the UK, particularly in Scotland and Northern England, "skulch" is a slang term for junk mail or unsolicited mail. It's often used to describe unwanted letters, flyers, or catalogs that clutter up your mailbox or doorstep.

For example, you might say: "I'm sick of all this skulch coming through the door every day. Can't they just leave me alone?"

The term "skulch" is thought to have originated from the Scottish word "skulk," which means to lurk or hide, possibly referring to the way junk mail seems to lurk in your mailbox or hide in your pile of bills and important documents.