Check the replacement line specification
Record the spool, line and cap markings before opening the head or selecting a compatible replacement.
Version 2.0.0. Required observations are marked *. Your answers stay in this browser.
1. Match the model and parts
Remove the battery. Find LST300 and the adjacent type number on the tool label. Compare the guard, cap, spool and assembly figures with the linked LST300 manual. Use ServiceNet for your exact type if they differ. LST300 is not a bump-feed head.
Region: US
Parts: Automatic-feed head with AF-100 spool; match model and tool type to manual
Not covered: LST420 / LSTE525; GH corded models; Dual-line heads; Metal line or blades; Nonmatching tool type or modified head; Unknown tool type or missing exact-type manual; Bump-feed conversion.
Choose the versions you can confirm.
Compare versions →2. Prepare
Keep the battery removed if the exact type/manual match is unknown or parts differ from the figures. Stop for a damaged battery, exposed wiring, a faulty switch, cracked guard, broken spool/hub, damaged cap tabs or housing slots. Use an authorized service center. Never open the battery, motor housing or charger.
Consumables and fit
| Item | Specification & fit | Do not substitute |
|---|---|---|
| Factory-wound replacement spool | BLACK+DECKER AF-100; 0.065 inch (1.65 mm) round nylon monofilament Original LST300 automatic single-line head, after exact tool-type/manual match | Bump-feed or dual-line heads; metal, serrated or heavier line; unverified replacement headsEnglish p9 Cutting line / Line feeding; Replacement accessories |
| Bulk cutting line | 0.065 inch (1.65 mm) round nylon monofilament Intact original AF-100 spool with the slot, adjacent anchor hole, arrow and fill recesses in figs P–R | Serrated, square, heavier or metal line; different anchor geometryEnglish p10 Rewinding spool from bulk line; figs P–R |
| Replacement spool cap | BLACK+DECKER RC-100, confirmed against the exact tool-type parts list Original compatible AF-100 housing with undamaged slots | Damaged housing; caps with different tabs; forcing an apparently similar partEnglish p9 Cutting line / Line feeding; Replacement accessories |
3. Follow your checks
Match the model and preparation to start.
Read all possible routes
Is the battery removed, the trigger released and the cutting head stopped, with no battery damage, exposed wiring or faulty switch?
- Yes — Keep the battery removed for every hands-on step.
- No — Stop using the tool for electrical, battery or switch damage. If you have only omitted battery removal, make the tool safe before restarting.
- Not sure — Keep the battery removed. Save your preparation record and check the matching manual before continuing.
Have you matched the label LST300 AND its exact tool type to the official lookup manual and its figures, with the original AF-100 automatic single-line head?
- Yes — Record the label type and matching manual reference in the first step.
- No — An unknown type, unavailable type manual, different figures, bump-feed head or dual-line conversion blocks this procedure. Use manufacturer support to identify the correct instructions.
- Not sure — Keep the battery removed. Save your preparation record and check the matching manual before continuing.
Can you read the actual spool or line package and identify its diameter, shape and material?
- Yes — Read every specification; color alone does not establish compatibility.
- No — Obtain a readable label or manufacturer part listing before fitting it.
- Not sure — Keep the battery removed. Save your preparation record and check the matching manual before continuing.
Does it specify AF-100 or 0.065 inch (1.65 mm) round nylon monofilament for the matching original head?
- Yes — Record the part details and choose a fitting method.
- No — Set aside serrated, heavier, metal or otherwise unverified line and obtain the correct specification.
- Not sure — Keep the battery removed. Save your preparation record and check the matching manual before continuing.
4. Follow and record
Complete the checks before recording physical work. Follow steps in order.
Record the exact tool and make it safe
Release the trigger, let the head stop, engage the lock-off and remove the battery. Leave it removed throughout hands-on care. Keep fingers away from the sharp cutter on the guard. Read LST300 and the tool type from the label. Open the official model/type lookup and compare its manual and parts figures with your actual guard, single-line head and AF-100 spool. A readable model name alone does not establish the type. If the exact type manual cannot be obtained, or any figure differs, save a preparation record and stop.
Look for: The battery is physically separate from the tool; your label type and matching manual reference are written below.
Manual: Official model/type lookup instructions; type is beside or below the model numberRead the replacement label
Read the actual package, not just a listing photo. For a factory-wound spool, check BLACK+DECKER AF-100. For loose line, check 0.065 inch (1.65 mm), round cross-section and nylon monofilament.
Look for: All required markings are readable and refer to the part you have.
Manual: English p9 Cutting line / Line feeding; Replacement accessoriesExclude incompatible cutting material
Set aside heavier or serrated line, metal cutting material and a spool intended for a dual-line or bump-feed head. Do not substitute a different line because it fits through the eyelet.
Look for: The selected line matches diameter, shape and material together.
Manual: English p9 Cutting line / Line feeding; Replacement accessoriesCheck the cap separately
If a cap is required, the manual lists RC-100. Match it to the exact tool-type listing and original housing, including both tabs. A correct cap does not make a damaged housing usable.
Look for: The cap marking and retention design match; no damaged tabs are being reused.
Manual: English p9 Cutting line / Line feeding; Replacement accessoriesChoose factory-wound or hand-wound line
The manufacturer recommends factory-wound spools for best results and notes that hand-wound line can tangle more often. Choose the spool-replacement task for AF-100, or the model-specific rewind task for an intact original spool and compatible bulk line.
Look for: Your choice leads to the appropriate installation sequence rather than mixing their anchor steps.
Manual: English p10 Rewinding spool from bulk line; figs P–RSave the compatibility decision
Record the markings and whether the part passed. Keep any incompatible part separate and leave the head closed until the correct material is ready. This task confirms supplies; fitting and a normal-use check are separate tasks.
Look for: The record identifies the actual consumable and the next fitting task.
Manual: English p9 Cutting line / Line feeding; Replacement accessories
5. Keep your result
Record what you observed. A completed checklist does not certify that equipment is repaired.
When to check again
Before buying or fitting cutting line, a spool or cap
Inspect when the stated condition occurs. The manual gives no fixed day or month interval.
Manufacturer guidance · English p9 Cutting line / Line feeding; Replacement accessoriesSources & fit
- BLACK+DECKER LST300 instruction manual (manufacturer document, retailer-hosted)English p9 Cutting line / Line feeding; Replacement accessories · Checked 2026-10-13
- BLACK+DECKER: locate a manual using model and type numberOfficial model/type lookup instructions; type is beside or below the model number · Checked 2026-10-13
- BLACK+DECKER LST300 product and supportLST300 model identity; Automatic Feed Spool; Includes AF-100 · Checked 2026-10-13
Independent, AI-assisted guidance. No physical repair trial is claimed. Manufacturer instructions for your exact version take priority.