Guitars and Bass bodies come in 2 categories...... carved top and flat top.
Type #1 looks like the picture above. The common 2 piece system found on Les Paul guitars and many others. This a 4 hole setup.
Type #2 is a combination of the 2 parts in type #1. The bridge part is married to the stop tail part. This "uni-matic" system is a bridge and stop tail piece in one. This is a 2 hole setup.
Type #3 is the bridge section only, like in the example to the left. This is called a string thru body. The strings pass over the bridge section and then go thru the body. This acts like the stop bar piece in Type #1. The ball ends of the strings are held on the other side of the body using string ferrules. This is a 2 hole setup.
If you have the very common 1 or 2 piece Tune-o-Matic bridge for a standard 6 string, using the common 3.25" stop tail piece, you should fully understand how each piece relates to the installation of a Kahler stud mounting system. The stud mounting models are best for all situations because they are designed for arched or flat top bodies and can attach to the Tune-o-Matic studs. They are better suited to accommodate the higher string height of a Tune-o-Matic as well as compensate for steep neck angles like on LP's. Almost all guitars that use a Tune-o-Matic bridges have a steep neck angle as opposed to a Stratocaster type guitar which has a flat shallow neck angle.
So here is the lowdown...
The stop tail piece is slid onto the 2 big slotted studs and holds the ball end of the strings . The Kahler mounts to these studs.
The bridge portion (the piece where string vibration stops) is between the stop tail piece and the bridge pickup. It has 2 holes in the wood for mounting. The Kahler uses the holes for a new purpose... riser wheels. They act as levelers. Because the tremolo is mounted "floating" off the body top, it needs to be leveled. You will have 2 or 4 holes to start with depending on the type of TOM you have. So you use what holes you have, and drill holes for what you don't have. You need 4 holes like in type #1. The 2 big screws are for the side hooks of the mounting frame. When screwed up or down, they control the level of the back of the tremolo. The thumb wheel under the front of the tremolo sticking out is a front leveler. it screws up and down, leveling the front. There is one on both sides. Will it fit properly? Read on to find out.
In the 80's, most guitars with Tune-o-Matic bridges, had a standardized installation location that was programmed into the routing machines at the factory and in those days, Kahlers were a drop on perfect installation. But since the late 80's - early 90's, the stop tail part of the Tune-o-Matic bridge has been shifted around like the grills on a Chevy over the years. The bridge part is always in the same place for the scale range of course, but the tail piece is not as important. It can go anywhere since all it does is hold the strings. Unfortunately the Kahler needs these studs to mount on and since they are no longer in a standardized locale, the studs sometimes need to be removed and relocated in the right spot. You need about 2-1/16" to about 2-1/4" between the bridge sections small E saddle notch (which should be set to the scale length) and the center/middle of the stop tail piece to be "in the ballpark" for mounting a six string stud mount system without having to relocate the studs. If you have the one piece wrap-around Uni-Matic, then you don't have a problem with relocation. This step can be skipped since you will be drilling fresh new holes for the rear studs and the install will look perfect. I always suggest a qualified luthier to do the job.
This is the stud mounting system that is mounted properly.
The other type of body is a flat top. It simply means the face of the guitar body is flat as a pancake. The stud mounting systems can fit on a flat top body as well, but only if it has a Tune-o-Matic, but if not, the flat mounting Kahler is better suited. The versatile flat mount is a perfect glove fit on most Stratocasters (right) and can accommodate any flat top guitar. Like the stud mounting models, It allows for plenty of intonation travel room, radius matching and string spacing to make any guitar player happy. It has a low profile and is the bomb for palm muting. Several adapter plates are available for Fulcrum to Kahler refits, as well as other difficult retrofits. If you prefer, a 7330 Fixed bridge will also work on any flat surface. With no route needed, just screw it down and string 'er up. See installation guidelines for more info.
As in all Kahler tremolos you must route a 1" inch deep (not thru body) surface cavity into the top of the body to accommodate the springs underneath the trem. See Routing
Most basses have fixed bridges on them and have no routing under the bridge, so once the bridge is removed you have a nice fresh, flat area to install your new bass tremolo or fixed bass bridge. There are some clearance issues to hurdle first before getting excited about installing a bass tremolo. The 7410, 7415 or 7416 bass tremolos are meant for flat top basses only, but you need minimum clearance of 1.750" (1-3/4" inches ) from the intonation line to the back of the bass to use properly. (picture left) 7440, 7450 or 7460 Fixed bass bridges require no routing and can mount on any flat surface. They have 4-6 screw holes in the mounting plate that match up with most inline bass mounting holes, particularly Fender Precision and Fender Jazz basses and other basses styled after them.