How can I copy files onto an SD card with a Honeycomb tablet? It seems like copying a file onto the SD card ought to be easy, but for the life of me I can't figure out how to do it. I have an (International) Motorola Xoom Wifi running stock Moto Android 3.2.

If I insert an SD card with content on it, I can see the contents of the card show up in the tablet's Gallery app. I can also go into the built-in Files app and browse the contents of the SD card. Using the Files app I can select files and copy them from the SD card to the internal storage.

However when I browse the tablet's internal storage with the Files app and select and Copy a file, if I then navigate to the SD card the Paste Here option is grayed out.

Using File Manager HD, I can't even find the SD card. It looks (from the Files app) like the SD card is at /mnt/external1/ but I can't see any way to get there. Is there something I'm missing in File Manager HD to find the SD card, or is there a deficiency in File Manager HD that another file manager could solve?

Also strangely I can delete files from the SD card using the gallery app, but not using the Files file manager app!
Getting to your external in File Manager HD is...not very obvious. The only way I'm aware of to get to it is to hit the Home button at the top right on the action bar (not the Android OS button in the bottom left) and then hit Up. This should put you at /mnt, so you can get to the external at /mnt/external1. The "Storage" shortcut on the left pane also takes me there, but I don't think it's always operated like that in the past. I might be mis-remembering there, though. If "Storage" takes you to /mnt/sdcard then you can hit "Up" from there to get back to /mnt.

As for copying, the external card was originally read-only by default. Now it seems to exist in some kind of weird limbo (at least for me) and I'm not entirely sure how the permissions are designed. File Manager HD shows its permissions as dr- (that is, read-only directory) but it lets me paste files there anyway. Nonetheless, if you're rooted you can use something like MicroSD Mounter as an easy way to remount it RW (it works fine for me).

I should probably also note that the above is on Android 3.2.2, after getting Verizon's LTE upgrade. The permissions may still be read-only for Xooms in other regions, but I'm not sure. Mine could also just be read/write because I'm using a custom kernel and boot image (don't remember if it was in there).