  Staple-shaped Wilson line operators are necessary for the study of transverse
momentum-dependent parton distribution functions (TMDPDFs) in lattice QCD and
beyond. In this work, we study the renormalization of such operators in the
general case of an asymmetric staple. We analyze the mixing pattern of these
operators using their symmetry properties, where we find that the possible
mixing is restricted within groups of four operators. We then present numerical
results using the regularization independent momentum subtraction (RI/MOM)
scheme to study the importance of mixing using one operator in particular, the
$\gamma_0$ operator. Based on these results, we consider the short distance
ratio (SDR) scheme, which is desirable in the absence of mixing. Finally, we
investigate a variant of the RI/MOM scheme, where the renormalization factors
are computed at short distances.
