user36889: I want to be able to create a rectangular mask in Premiere Pro where I can type in how many pixels wide and how many pixels high it will be.
This question is similar, but I've tested the technique in the answer (which is also the best I've found on YouTube) and it seems that the new Premiere Pro update has done away with the shift-click-and-drag way of snapping the mask to a rectangular shape. Besides, I wouldn't be able to get the mask pixel-perfect with any manual method.
While it's possible to enlarge a mask while keeping it a perfect rectangle, Premiere Pro seems to have its ratio locked.
What I'm trying to do, ultimately, is mask rectangles of video, where I decide exactly what shape the rectangles are, and then use the masks to round off the corners. I also want to be able to animate the masks so that the video grows and slides around the screen, maintaining the rounded corners. And I want to be able to position these masks precisely too.

user4426: I don't think this is possible in Premiere, or at least not simple to do.
You'd think you could create some rulers, right click on them, enter some values, then create a shape and snap the corners of the shape to the rulers, but it doesn't work.
I suspect this is one of those product differentiation things where Adobe has decided to restrict some features in Premiere so as to keep some in After Effects.  Whether this is deliberate or they just haven't programmed the features into both apps yet, I don't know.
Essentially, if you want to do stuff like this, use After Effects.
(Not a great answer, sorry.)

36889: <p>I want to be able to create a rectangular mask in Premiere Pro where I can type in how many pixels wide and how many pixels high it will be.</p>
<p><a href="https://video.stackexchange.com/questions/16694/in-premiere-cc-how-do-you-create-a-tall-rectangular-mask">This question</a> is similar, but I've tested the technique in the answer (which is also the best I've found on YouTube) and it seems that the new Premiere Pro update has done away with the shift-click-and-drag way of snapping the mask to a rectangular shape. Besides, I wouldn't be able to get the mask pixel-perfect with any manual method.</p>
<p>While it's possible to enlarge a mask while keeping it a perfect rectangle, Premiere Pro seems to have its ratio locked.</p>
<p>What I'm trying to do, ultimately, is mask rectangles of video, where I decide exactly what shape the rectangles are, and then use the masks to round off the corners. I also want to be able to animate the masks so that the video grows and slides around the screen, maintaining the rounded corners. And I want to be able to position these masks precisely too.</p>
 4426: <p>I don't think this is possible in Premiere, or at least not simple to do.</p>
<p>You'd think you could create some rulers, right click on them, enter some values, then create a shape and snap the corners of the shape to the rulers, but it doesn't work.</p>
<p>I suspect this is one of those product differentiation things where Adobe has decided to restrict some features in Premiere so as to keep some in After Effects.  Whether this is deliberate or they just haven't programmed the features into both apps yet, I don't know.</p>
<p>Essentially, if you want to do stuff like this, use After Effects.<br />
(Not a great answer, sorry.)</p>
