A letterbox that howls is usually the brush
I stood in the hall in January and the letterbox howled. A thin, hard note when the wind hit the front door. I thought the door had dropped. I put a hand on the flap. Cold air came through in a slab. The inner brush was a bald strip. The outer flap sat open a finger's width because one spring had gone. The door was fine. The hole in it was not.
A letterbox is a slot with a flap on the outside and, if you are lucky, a flap or a brush on the inside. The brush is a pile that closes the slot when the flap is shut. Post still goes through. Wind does not. If the brush is worn, missing, or fitted only on one lip, the slot is a whistle. People buy a new door. I change the brush, and I look at the flap.
A loft hatch that dumps heat is usually the catch is the hole in the ceiling. Same idea. A lid that does not sit dumps air. A dust sheet that leaks is usually the gap at the skirting is a gap you left at an edge. The letterbox is an edge you walk past every day. I check the slot before I blame the frame.
When I check I open the inner flap, if there is one, and I look at the pile. Bald, matted, or hanging off one screw is the job. I look at the outer flap. It should fall shut and sit on the face. A flap that stays up is a spring, or a hinge pin that has walked. I also look at the screws. A letterbox plate held only in the skin of a thin door will rattle and then the brush cannot meet. I want the plate tight, the flap free, and the brush filling the slot.
I fit a brush that spans the opening, not a short strip that leaves two corners open. Those corners howl first. I do not block the slot with foam. Post has to come in. A second inner flap behind a good brush is extra, not a substitute for pile that has gone.
Skip a new door because the letterbox sang. Skip tape over the slot in winter and then forgetting it in April. Skip a brush meant for a draught excluder under a door, cut short and jammed in. It sheds and then it jams the post. Skip painting the flap so it sticks open. Skip tightening the plate until the flap cannot move. Tight on the door, free on the hinge.
UK year is the first hard wind after the clocks go back. I now stand in the hall on that night and I listen. If I can hear the slot, I do the brush before I buy another roll of anything for the loft.
I also look at the mat. A wet fan of rain under the slot is the same gap. The brush that stops the howl stops that too, if the outer flap sits.
I do not need a new front door because the letterbox howled. I need a flap that shuts, a brush that fills the slot, and screws that hold the plate to the door.
If I later add a buy link here, it will be a paid promo.