What are some alternatives?
When comparing Terrastruct and UI Movement, you can also consider the following products
SnapUp - Wireframe faster / create amazing user interfaces
UI Garage - Specific mobile and web design patterns for your inspiration
Plectica - Easily diagram anything, together
UI Interactions - The best UI Interactions for your inspiration, every day.
Whimsical Wireframes - Lightning fast wireframing with real-time collaboration.
UpLabs - The best material design, iOS & web resources, every day