  The nucleon is described as a bound state of a quark and an extended diquark.
Hereby the notion ``diquark'' refers to the modelling of separable correlations
in the two-quark Green's functions. Binding of quarks and diquarks takes place
via an exchange interaction and is therefore related to the Pauli principle for
three-quark states. Fully Poincare covariant nucleon amplitudes are calculated
for free constituent propagators as well as for dressed propagators which
parameterise confinement. The corresponding results for space-like form factors
differ quantitatively but not qualitatively for various ans\"atze for the
propagators. These results do not allow to draw definite conclusions on the
permissibility of different dressing functions. Results for kaon
photoproduction, on the other hand, exclude a whole class of constituent
propagators.
