A pseudodiagram is a diagram of a knot with some crossing information
missing. We review and expand the theory of pseudodiagrams introduced by R.
Hanaki. We then extend this theory to the realm of virtual knots, a
generalization of knots. In particular, we investigate how much crossing
information must be known to conclude that a diagram is a diagram of the unknot
(the trivializing number). We provide a table of trivializing numbers for knots
with no more than 10 crossings, as well as an algorithm to calculate an upper
bound on the trivializing number of any knot.