Dolmetsch 'Nova' tenors and basses are supplied with a small plastic bag of spare parts. These include the thumb rest and screws for fitting it.
Fitting the thumb rest is a fiddly job and I have taken it upon myself to do it for my clients. There are five possible positions about 3mm. apart and I select the one next to the top as this seems to me to be the best option. If you don't like my choice you can move it yourself. In the image you can see where the thumb rest was fitted by the distortion of the holes caused by the screws. You should use a small 'cross point' screwdriver. (Not essential, but its the right tool and makes the job easier.)
There are no difficulties with the bass but you should note the following points for many of the tenors. For a time the supplied screws were too long. (The latest batches of recorders have the correct screws.) They will not hold the thumb rest tightly and they will protrude into the bore of the recorder if you force them. I have ground down the screws I use to fit the thumb rest. Because this removes the taper at the tip they can be difficult to start into the hole. The answer is enlarge the entry to the screw hole by gently twiddling the cross point screwdriver into it before presenting the screw. This action opens out the top of the hole just enough to make the job easy. If you lose one of the shortened screws and cannot shorten one yourself you can send me the other spare screws with a stamped and addressed envelope for their return and I will shorten them for you without charge. The shortened screws are 6.5mm. long, over all.
I have never needed to use any of the other parts, pads, axles and springs.
2017 Update! Some tenors have arrived with their foot joint keys fitted with the same size axles as the body keys. These are too short and, if they are fully tightened, result in the axle only being held at the threaded end. The slotted end being no longer in the hole through the buttress. The result is floppy key action that never seals the holes properly. If you have been unlucky enough to acquire one of these tenors you may find screws of the correct length in the bag. If you do not it is just possible to correct the key action by unscrewing the axles so that the slotted end is wound back into the hole. (After I discovered this problem I made sure that all the tenors I supplied were fitted with the correct screws.)
I have a few replacement keys.
If you lose the bass sling a standard sling will do the job.