"Basically"....It's a block of aluminum ...the same size as the mold. It has a sprue hole and an alignment pin, runner and the necessary vents. The plate is flat...except for the sprue hole, runner, pin and the vents.

You clamp the plate on 1/2 of the mold....in the case of the Swim Shad it is the bottom of the bait. The plate is flat...so you can only get plastic to the bottom half of the the mold. Basically you are shooting 1/2 a bait.

After injecting the bottom of your bait, You unclamp the plate, trim off the runner...and close the mold back up (you have a bottom of the bait....just like if you hand poured it). Now you have a regular mold set up..with half of it already full. Inject the top half...and WOW!
It's pretty fast...while you're waiting for the bottom to set...I'm heating (or reheating) the top...while demolding...I'm reheating the bottom...on and on!
Yes...you can do the same thing hand pouring...IF you are good enough to do it (I'm not)...plus this gives you a really nice straight line between the two colors.
Make sense???