IBM 3590 - Manual (Page 110)

Leader Block Replacement
Figure 22 illustrates the replacement procedure.
The following lists the components required to replace the leader block:
1 Leader Block 2 Cartridge
3 Clutch Tool 4 Guide
5 Attachment Tool Cavity 6 Guide Groove
7 Attachment Tool 8 Insert Pin
9 Insertion Lever
Perform the following steps to replace the leader block when it has separated
from the magnetic tape. See Figure 22 for component locations in this
procedure.
Figure 22. Leader Block Replacement Procedure
90 3590 Operator Guide