Father Christmas has a special key that can enter any home without a chimney. It is made by the elf blacksmith, Ambolt in his forge from a magic metal called Metalmorphosis, mined by the elves in Lapland.
Sometimes children leave their own Magic Key out for him with the following rhyme;
“Father Christmas, please help me.
I have no chimney, just this key
And though the lock’s a little tight
I know you’ll make it fit just right
I’ll leave it out on Christmas Eve
And dream of gifts I hope you’ll leave”