You will be able to see the liquid fill the gap as you go along. Do not remove the pins when you come to them, instead "jump over" the pins as you go along. You will see the Weld-On fill in around the pins. When you get to the end of the pieces, wait about 30 seconds, then remove the pins. Since the tape is holding it, the vertical piece should remain in place. You will have a few seconds where can gently slide the vertical piece a bit to align it, but do not pick up the vertical piece as this will create bubbles in the joint. Hold the vertical piece in place for about another minute. Do not move the pieces again for at least another 4 hours.
Once you have perfected your bonding procedure, it's time to go on to the real thing. What we are going to do first is bond the 2 side pieces to the back piece of the refugium. It will look like this just before you start injecting the Weld-On #4 into the joints.