when going between screen sizes, do people usually just resize the frame for the prototype?

[heavy nimbus]

or is there something that automatically does it for you?

this is as in: i have build something for an android and want to test it on an iphone (e.g.)

[dry jacinth]

For going from andorid to iphone where the size is just slightly different (so the layout wouldn't really change much) I would just manually resize it. You can do it by manually dragging the edges, or you can press 'k' and then scaling wise do it. The latter might not be good though just because it might also change the font sizes and stuff that you might not want.