Answer to Question 1
A weld that is done on-site
Answer to Question 2
Fixed pins are used for images that tile: bricks, wood, stone, etc. These pins are used to adjust the image's start point or location, size and scale, rotation angle, and distortion. Free pins are used for stand-alone images, such as a specific door photo that needs to fit within a door face.
Q: When saving a SketchUp model of a painting or other model that should align with walls when imported, what do you need to do to set its alignment properties?