How to Wind a Trimmer Spool — Single-Line and Dual-Line (From the Manuals)

Winding your own spool works, but the makers are candid about it: BLACK+DECKER’s manual says hand-wound spools are likely to tangle more often than factory-wound ones. Whatever the head, three rules repeat in every manual — use the line size your manual lists (see trimmer line size), wind in the direction of the arrow on the spool, and wind neatly in layers without criss-crossing. The details differ by head.

Before any of these: remove the battery pack, take the spool out of the head, and remove any old line left on it.

Single-line auto-feed spools (BLACK+DECKER AF-100, CRAFTSMAN CMZST065)

From the BLACK+DECKER LST400/LST420 and CRAFTSMAN CMCST900 manuals — both .065” round line only:

1. Make a fold about 3/4” (19 mm) from the end of the line and feed it into one of the line-anchoring slots.
2. Push that 3/4” end into the hole in the spool next to the slot, and pull the line tight against the spool.
3. Wind the line in the direction of the arrow on the spool — neatly, in layers, no criss-crossing.
4. When the wound line reaches the recesses on the spool, cut it.
5. Refit the spool as in the spool-replacement steps (AF-100 guide, CRAFTSMAN guide).

RYOBI single-line spools (P20015 18V)

From the RYOBI P20015 manual (“Line replacement”):

1. Cut about 9 ft. of line — 0.065” round or twisted, or 0.080” twisted.
2. Insert the line into the anchor hole in the upper part of the spool.
3. Wind clockwise, as the arrows on the spool show.
4. Put the line in the slot on the upper spool flange, leaving about 6 in. beyond the slot.
5. Don’t overfill: leave at least 1/4 in. between the wound line and the outside edge of the spool.
6. Refit the spool — see the RYOBI spool guide.

Dual-line spools (Toro 51831 / 51831T)

From the Toro manual (“Replacing the String”) — 2 mm (0.080”) line only:

1. Cut one piece of line about 3 m (10 ft) long.
2. Bend it at the midpoint and push the bend into the starter slot in the center rim of the spool until it snaps in.
3. Wrap both halves evenly and firmly — clockwise when you look at the bottom of the spool.
4. Leave just enough to reach the swath blade and snap the two ends into the guide slots on the spool.
5. Put the spool in the cover and route the ends through the holes — see the Toro 88616 guide.

Sources: BLACK+DECKER LST400/LST420 instruction manual, “Rewinding spool from bulk line”, p. 10 (PDF); CRAFTSMAN CMCST900 instruction manual (NA473221), “Rewinding Spool from Bulk Line”, pp. 8–9 (PDF); RYOBI P20015 operator’s manual, “Line replacement” (PDF); Toro 51831/51831T operator’s manual (Form 3440-153 Rev D), pp. 16–17 (PDF). Checked September 25, 2026.