Eye Knife

Does anyone know the young adult book about dragons and a knife that cuts a triangular door?
He finds the knife in the potato field where he lives. There is a bible quote, from Psalm about ‘thou hast forsaken me and cast me into the place of dragons. When he is in the dragon world, the people there can’t pick up the cardboard triangle, only he can. Also, there is some strange area between the worlds where it’s all misty/foggy, and that was what I remember from the book coverart: a foggy plain with a triangle door, and a bright eye gleaming through it. I remember that the book coverart characteristics look alot like ‘The Forgotten Door’, and ‘Jeremy Thatcher, Dragon Hatcher’. I don’t think either author wrote this book, but it certainly could have been published by the same company.
OK, I’m glad to see you reposted this, because I think I found the answer!
The book “Beyond the Open Door” (alternate title “With My Knife”) by Andrew Lansdown has this summary: “Colyn uses the weird knife he got for his birthday to cut a hole in a cardboard box which turns into a doorway to another world– a world surrounded by mist and dragons! When a hole that he makes in a cardboard box turns into a doorway, Colyn discovers, to his amazement, that he can neither close the hole nor shut the doorway.” Here’s a link to the cover of “Beyond the Open Door”: http://i7.ebayimg.com/03/i/04/3f/6f/a8_1_b.JPG
I hope that’s the right one!
Here’s a link to a bunch of inexpensive copies for sale: http://www.amazon.com/exec/obidos/ASIN/0590471600/24680e-20
The Horrors – A Knife In Their Eye (Live)