Depends...what are you wrapping in?
I used to use the Texas crutch back in the day and would wrap in foil.
With that, I had large pro kitchen sized rolls of foil (from Sam's or Costco)...I pull off two fairly long sheets of it and in the middle, I'd fold the two inner seams together a couple times and that would "lock" them together and then I'd roll and wrap my brisket pretty air tight.
With butcher paper that I"m now using, I don't go for "air tight"...I peel off a couple of long sheets of the red butcher paper I got at Costco..Im guessing 16-18" wide...and overlaps them on my wrapping table.
I pour a little tallow I"ve rendered out from the trimmings of my brisket on first, and put fat side down....I then wrap it, rolling the meat along, tucking in the edges as I go...and finish with fat cap up.<P>
Again, I'm not going for air tight here...the tall and other fat coming out of the meat as it continues to cook then rest, to me..."seals" the package enough for me.
With paper, as I understand it, the idea is to have it "breathe" a bit in there so as to help preserve bark.
Some one please correct me on that last part if I got it wrong....
HTH,
cayenne