  We try to give a geometric construction of 3d $\mathcal{N}=2$ gauge theories
using three-manifolds and Dehn surgeries. It is known that wrapping M5-branes
on plumbing three-manifolds leads to 3d theories with mixed Chern-Simons
levels. We find that this construction can be extended by adding Lagrangian
defects on the tangent bundles of three-manifolds. After wrapping M5-branes on
these defects and through M-theory/IIB string duality, one can get D5-branes
that introduce chiral multiplets. This is analogous to Ooguri-Vafa construction
of Wilson loop operators along knots on the three-sphere. In this note, we only
consider unknotted matter circles, which are intersections between defect
M5-branes and plumbing manifolds. After introducing matters, mirror dualities
of 3d theories match with Kirby moves of plumbing manifolds. We also find the
dictionary between various structures of three-manifolds and physical aspects
of 3d gauge theories.

High Energy Physics - Theory;Geometric Topology