Need a Seam Down the Middle

See how that wall is 38″ wide? And the bolt of grasscloth is 36″ wide?
So two strips of wallpaper are needed to cover this wall.
You don’t want a 36″ wide piece and then a 2″ wide piece. Much better to have both strips the same width. This makes each strip 19″ wide, with a seam centered down the middle.
Much more pleasing to the eye.
Note that it does take extra paper to do this, because the 17″ wide leftover strips can’t be used anywhere else.
But the overall visual symmetry is worth it.

Store Leftover Wallpaper in the House (Not Garage or Attic)

These homeowners had damage from Hurricane Harvey and needed to replace two strips of grasscloth. They brought the box of leftover paper in from the garage – and discovered that paper was ruined. Water had gotten onto the garage floor, soaked the box (which was sitting on the floor) and wicked up into the ends of the paper. Some of it was even mildewed.

Moral: Always store left over paper in the house, under climate-controlled conditions. Never the garage or attic.

Color Difference Due To Fading Over The Years

I hung this original paper more than 15 years ago. Some areas had become stained, so I was called to fix it. Luckily, the homeowner had saved the left over paper, so there was enough to replace the damaged strips.

You can see a slight difference in color between the strip on the left, which was hung 15 years ago and has been exposed to light all that time, and the strip on the right, which has been stored in a dark closet until I put it up today.