Abstract: An improved wedge is provided for a septum and wedge subassembly in a fluid path of a fluid delivery device such as for use in a catheter insertion mechanism of a patch pump. The wedge has a retaining edge to provide axial force to retain a septum therein to obviate need for additional insertion mechanism components to retain the septum in place as a needle passes therethrough to facilitate insertion of a catheter and then retracts. The retaining edge can be rolled or flanged to extend at least partially over a surface of the septum. The wedge is also configured to provide radial compression on the septum to achieve a sufficient needle and septum interface seal to withstand a filling pressure of the fluid delivery device.