One piece shims are installed with the beveled side down. Two piece shims are installed with the bottom shim rounded side down, top shim we suggest rounded side up! Use an installation tool such as a Phillips head screw driver to keep the shim in the proper orientation all the way to the bottom of the bore. Note that the shims are only slightly smaller than the lifter bore and that the bore seems to be very slightly tapered at the top!
The 1 piece shims can not be installed at an angle, they must be inserted perfectly square with the bore opening and then once inside the bore they will slide to the bottom. Two piece shims, because they are much thinner are easier to install but still should be square to the bore when inserted.