Don"t Hammer on the Door!

[Sailon1]

Questions: what is the small door/gate called on the mast where the sliders feed into?

Where can I find a replacement for the small door/gate on the mast that I tried to adjust with a hammer? Cost of this door? (Photo attached.)

The sliders (on the new mainsail) are catching on the portion of the track that is partly formed by the closed door/gate. There is a very small section--about 1/16 of an inch on the door--that does not line up with the track on the mainsail, hence, the sliders jam, more so on the way down rather than when sail is being raised.

Well I tried tapping on the edge of the door to line it up with the track. The door appears to be made out of lead and is somewhat brittle, and a piece of it broke off. The dimensions are 1 3/4 in. x 2 3/4 in long.
Who might carry such an item?
Thank you in advance for your input. Yes, I know, don't hammer on the door.

[Calif.Ted]

What you are looking for is a "mast gate" or mainsail gate I believe.
MetalMast Mainsail Gates

[Sailon1]

Thank you for the information that's a good start!