Fixing the Z721 knurled door handles requires a reasonable amount of diy skill.
You will be supplied with a couple of sleeve bolts and some self tapping screws. The sleeve bolts are for hollow doors and can fit through the holes in your latch, provided your latch has these. You may need to cut down the threaded part to accommodate a shallower door.
A couple of pointers before you get started.
The rose is threaded and as this is a fine thread be careful to ensure you unlock them the correct way, as they can tighten into a lock position making it difficult to unscrew. It is also easy to cross-thread so ensure you get the right feel to locate the thread when you have released the rose completely. To unscrew the threaded rose always unscrew in an anti-clockwise direction viewed from the front of the handle (as if on the door). A firm grip and jolt will be need to release them if you do turn the rose in the wrong direction.
You will need a 2mm drill. This is needed for the screws to stop them binding or even breaking. Always run a screw into the wood gently to start with until you get the required torque to sufficiently tighten down. Some woods like hardwood will need you to run the drill several times and to use a slightly larger 2.5mm drill bit. In some cases a little bit of candle wax around the screw thread will also help avoid screws jamming and breaking. Do not screw directly into the door without first drilling these pilot holes.
The design of these levers (t-bar) is such that the rose collars will not be releasable over the lever itself. This makes things a little more uncomfortable when driving the fixing screws into place. This makes the case for ensuring you mark out and drill the pilot holes in the correct position before starting.
Fixing the Z721 to the Door
Place the levers onto the door with the spindle and allow the levers to fall loosely to their true line before then marking the fixing positions for the screws and bolts. Check from the side of the door that the levers look to be inline and are not sloping or at an angle. Fixing interior door handles that are out of line can tighten the lever action causing them to stick when fitted.
If the holes are not already in the door for the sleeve bolts you will need to drill these through (check the latch has provision for the bolts to pass through before drilling). This just needs to be a clearance hole sufficient for the bolts to pass though. You can then screw clamp the two levers to the door with the sleeve bolts first and then use the self-tapping screws to get a more solid fixing. With the sleeve bolts in place this will be easier to do. When using screwdrivers please ensure a suitable Philips type head is used as the screw heads are smaller to allow them to sit down in the countersunk positions in the rose itself.
Refit the rose covers over the levers and tighten in a clockwise direction. To avoid cross threading the rose covers always start it carefully and release in a back and forth direction until you pick up the thread and the rose will then easily tighten to its closed position. The rose does not need to be tightened too hard as it is unlikely to loosen but if it does it is simple to tighten back again. Remember to unlock the rose thread by turning in an anti-clockwise direction.
Once you are happy that everything looks correct and the levers are retruning on their springs correctly all you need to do is tighten the grub screws under each lever for a real solid fixing that will last for years to come.