Solid trimming

Help please - I have a curving wall, with joists running up to it. The joists are all solid groups, and 10" x 2". At the moment they are all made the same length i.e. too long.
I want to trim them so that they meet the solid wall, so they will necessarily all be different lengths. I can’t work out how to do that using the Solid Tolls options. It seems i have to trim the joists one at a time?? I made a solid curved wall and Union deletes the wrong bit of joist, so i made a negative of the curved wall ( a solid where the wall “isn’t”) and it deleted the right bit of joist but the remainder is whole through the negative curve…
Sorry. maybe too much explanation…?

Sorry, Subract, not Union…

Solid tools will only work with two solids at one time, so it can be a bit tricky to multiple trims.
If they are indeed all different lengths and groups not instances of a component, you can group all the joists together, then explode them so they are loose geometry within a single solid group and then use that with your wall solid. You can return the loose geometry back to groups when done. The is a plugin for that, Loose to Groups.

But seeing your model would give us a better chance of offering an appropriate solution.

Here are two options with a very basic model.
The first just means repeating the Trim action 10 times.

If it was something more complex I would probably use the grouped groups method.

thanks. now i understand. so i grouped all the joists into one solid group, and subtracted the ‘negative’ group.
i’ve just looked and your second animation looks pretty much the same as mine!