+0
When pack tonight, make sure you tape the boxes shut and label them.

Whend pack tonight, make sure you tape the boxes tight and label them.

Do both of the above versions sound right and good? Thanks.
+0
AngliholicWhen packing tonight, make sure you tape the boxes shut and label them.

When packing tonight, make sure you tape the boxes tightly/securely and label them.
Hi Angliholic
I've made a few small changes.
+0
Not the same meaning:

shut: close the boxes, don't leave any openings
tight: make the tape bind them tightly
Students: We have free audio pronunciation exercises.
Comments  
Yankee
AngliholicWhen packing tonight, make sure you tape the boxes shut and label them.

When packing tonight, make sure you tape the boxes tightly/securely and label them.

Hi Angliholic

I've made a few small changes.

Thanks, Yankee, for the correction.

There is no room for doubt that your suggestions are excellent.
 Marius Hancu's reply was promoted to an answer.
Teachers: We supply a list of EFL job vacancies
Thanks, Marius, for the useful extra info.