New Zealand 'Lord of the rings'
(sheet stamp is the top stamp)

A lot of countries issue the same stamp set in sheet and self-adhesive format. In a lot of cases it is easy to tell the difference, one type is smaller than the other (like the 2001-2003 New Zealand 'Lord of the rings') or a different shape (like the 2009 Canadian 'tourist attractions') etc. Occasionally, both sets of stamps look the same (like the 2010 Canadian 'animal photography'). If you think of how you buy the stamps you can see how to tell the difference. A sheet stamp will have been torn away from the rest of the stamps on the sheet whereas the self-adhesive stamp has been die cut on it's backing paper and you then peel it off when you want to use it. If you use a magnifying glass to look at the edge of the stamp closely, you will see the torn paper fibres on each tooth of a sheet stamp while that on the self-adhesive stamp is clean cut.

Canadian 'Tourist attractions'
(sheet stamp is on the left)