First the ownership and privileges. At least in UNIX-based file sysems, all files and directories are assigned an owner and group. Depending on how your web server is configured, it may be important to have the owner and group set correctly. Likewise, files and directories have privileges assigned to owner, group, and everyone. Once again, depending on how your web server is configured, these may need specific values. You can read a little more about these here: http://www.dartmouth.edu/~rc/help/faq/permissions.html
When you install attforblock it should be placed in <moodle directory>/mod/ folder. The Plugin info should show:
mod_attforblock
In this case you first see the icon for attendance. Attendance is the name of the module and it has a physical path of <moodle directory>/mod/attforblock. The <moodle directory>/ is taken for granted and the / is replaced with a _ in the path listing shown here. The attendance block is installed in <moodle directory>/blocks folder so it shows up as:
block_attendance
(Don't ask me why "blocks/attendance" turns into "block_attendance" in this one!)
Richard