Especially around the pushpit and pulpit areas there often are stainless steel rods on bord of leasure vessels. My sailing yacht carries 25 mm rods which are in widespread use.
As I try to avoid drilling holes in any part of the vessel I consider this mounting bracket a convenient, fast and retreatable way of mounting easily accessible items to the vessels structure.
For tightening the bracket you will need 4 stainless steel screws and nuts M4 x 40 mm.
Obviously this thing cannot be an end in itself but offers a base on which all sorts of applications can be attached. Possible use cases include a multitude of mountings e.g. for dinghy motors, life saving appliances, fenders, mooring lines...
For durability in outdoor use, this part should be printed with ABS or some other robust material.