Flank Builder

 is a Tier 4 Tank that upgrades from Trap Guard and Builder at level 45.

Design
The has the same slightly-elongated Basic barrel in front as Trap Guard, but has its rear trapper replaced with a Builder barrel. This barrel looks identical to the one found on Builder itself.

Technical
Uniquely, the Flank Builder's blocks fly forwards to the mouse, not to the equivalent distance behind.

As the

 * Since your blocks go forward, you can treat this as a version of Fort with stronger Bullets and delayed Blocks.