In article , John Bartley
wrote:

Well, you've seen the post with a link to my first photo, which was very
much out of focus and (I think) overexposed. This evening, I had almost
exactly the same conditions as far as weather and light and clouds etc,
so out I went with my camera, spent about 20 minutes working with the
focus, tilt and swing. I even wore my glasses, and used a magnifier to
see the ground glass. When I was done, you could read the license plate
numbers on the trucks!!! I put in the film holder, pulled out the dark
slide, snapped the picture and went to put the dark slide back in - NO
GO!! Aaarrrg! [...]

John, what you experienced is pretty common with new LF users. You
accidently loaded the film so that it slid down the rails right under the
dark slide. As you discovered, once out of the holder, the film pops up
and blocks the slide.

Next time when you load the film feel free to use both hands to feel the
film down from the very top, then down the narrow retaining rails. Once
the film is in, you should be able to only bend/lift the very upper left
(notch) corner of the film.

Not to worry. We've all been there!