  New extended interpolating operators made of quenched three dimensional
fermions are introduced in the context of lattice QCD. The mass of the 3D
fermions can be tuned in a controlled way to find a better overlap of the
extended operators with the states of interest. The extended operators have
good renormalization properties and are easy to control when taking the
continuum limit. Moreover the short distance behaviour of the two point
functions built from these operators is greatly improved. A numerical
comparison with point sources and Jacobi smeared sources on dynamical 2+1
flavour configurations is presented.
