Thaumathurgic veils are immobile.
Evocation veils provide a two-way block worth half its value unless you add 2 shifts to make it transparent from inside. Glamours don't have this down-side.
Glamours can be used as a block, but they are actually supposed to be used as a stealth replacement. Which means, you only roll your glamours when someone rolls alertness to spot you. It's an opposed roll.
Basically, you say, "I sneak in"
Then, when appropriate, someone will roll to spot you and you will roll to not be seen. But instead of using stealth, you use discipline or deceit.