rv.xml

<android.support.v7.widget.RecyclerView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="@dimen/smaller_margin"
            android:orientation="horizontal"
            app:layoutManager="@string/linearLayoutManager"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@id/fifthCard" />