This sump is made with 3/8" acrylic and is a rimless sump.  Rimless provides greater access to the various areas, but it doesn't help keep saltcreep in the sump and off the woodwork of the stand.  

Dimensions: 40" x 14" x 16" (holds 34 gallons to the top)

The sump holds the ASM skimmer, a refugium, a LR zone, bubble trap & float switch to maintain the water level.

This sump is built with 3/8 acrylic, and a top flange was unnecessary as it maintained its shape perfectly.

The area under the teeth is a live rock zone, right before the bubble trap. Water from the refugium and from the skimmer section will pour into this area before it travels to the return section (on the left).

A top view allows you to see the refugium in the rear of the sump. 25% of the water will drain into the refugium.

Water will enter in the rear corner behind the skimmer. 

The small chamber is 2.5" by 2.5". Water will drain into this spot to trap the majority of the bubbles. It will then overflow into the skimmer section, then over the baffle into the LR zone. Next, water travels through the bubble trap, and into the return area where it can be pumped back up to the tank.

The sump was drilled for a 1.5" bulkhead so an external return pump could be used. The bubble trap baffles are 1" apart, with the center baffle 1.5" off the floor of the sump.

A float switch bracket is mounted in the back corner, well above the bulkhead. An elbow can be inserted into the bulkhead to draw water from the lowest point in the sump.  At the very least, a strainer should be installed to avoid anything big getting sucked into the return pump.