Can it be partially opened/closed?

The EVOm and EVOe locks into place in both open and closed positions. The roller shutter is locked into place on the load bed and is released via a pull strap, so suitable for large loads. Just be aware though, nothing should be touching the metal canister underneath, anything leaning on that could risk damaging it. The EVOe simply won't work if there is something touching the canister. The troubleshoot diagnosis will flash to say something is in the way.

The roller shutters stops every 30cm on the load bed and the locking pins can keep it in place, but it's not really suitable for when driving (a bump or pothole in the road will release the locking pins) - in short you can have it partially open for big loads but it's not locked into place.