    /*
     *  call-seq:
     *     dir.make_lock(lock_name) -> self
     *
     *  Make a lock with the name +lock_name+. Note that lockfiles will be stored
     *  in the directory with other files but they won't be visible to you. You
     *  should avoid using files with a .lck extension as this extension is
     *  reserved for lock files
     */
    static VALUE
    frt_dir_make_lock(VALUE self, VALUE rlock_name)
    {
        VALUE rlock;
        Lock *lock;
        Store *store = DATA_PTR(self);
        StringValue(rlock_name);
        lock = open_lock(store, rs2s(rlock_name));
        rlock = Data_Wrap_Struct(cLock, &frt_lock_mark, &frt_lock_free, lock);
        object_add(lock, rlock);
        return rlock;
    }