Check a spool cap that will not latch
Inspect both retaining tabs, clear the slots and correct spool or line seating before considering a replacement cap.
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 |
|---|---|---|
| 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.
Do the cap and housing match the exact-type manual and RC-100 specification?
- Yes — Check the two retaining sides separately.
- No — Identify the correct cap before trying to fit it.
- Not sure — Keep the battery removed. Save your preparation record and check the matching manual before continuing.
Are both cap tabs and housing slots intact, without cracks or distorted plastic?
- Yes — A seating problem may be corrected by cleaning and alignment.
- No — Broken retention parts need the correctly matched replacement or service; do not tape the cap down.
- 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 numberInspect both retention points
Remove the cap by pressing its tabs. Compare each tab and each housing slot with fig O. Note trapped grass, a line caught under the cap, or a spool sitting high; do not bend the tabs.
Look for: Each retaining point is intact and the obstruction, if any, is visible.
Manual: English pp9–10 Replacing the spool; figs M–OClear the slots and rim
Remove loose dirt and grass from the housing rim and slots. Keep the feed lever in place. If the lever is displaced and its fig N position is unclear, stop before refitting the spool.
Look for: The cap seating surfaces are clear and the lever position is known.
Manual: English pp9–10 Replacing the spool; figs M–OCorrect the spool and line position
Guide the single line through the eyelet. Set the original compatible spool on the boss and rotate it slightly until fully seated. Move any line away from the cap rim.
Look for: The spool rests fully down and no nylon crosses the cap seating surface.
Manual: English pp9–10 Replacing the spool; figs M–OAlign and snap the cap
Match both tabs with their slots and press the cap onto the housing until it snaps securely into place. Do not try to overcome resistance by striking the cap.
Look for: Both tabs engage; a click on only one side is insufficient.
Manual: English pp9–10 Replacing the spool; figs M–OCheck retention and record the result
Gently check that the cap remains attached without holding its tabs in. Record whether cleaning or seating resolved the problem. If it still will not retain, keep the battery out and obtain service or a confirmed compatible cap.
Look for: The cap stays retained on both sides, or the tool is clearly left out of use.
Manual: English pp9–10 Replacing the spool; figs M–O
5. Keep your result
Record what you observed. A completed checklist does not certify that equipment is repaired.
When to check again
Cap will not snap securely or was removed for line care
Inspect when the stated condition occurs. The manual gives no fixed day or month interval.
Manufacturer guidance · English pp9–10 Replacing the spool; figs M–OSources & fit
- BLACK+DECKER LST300 instruction manual (manufacturer document, retailer-hosted)English pp9–10 Replacing the spool; figs M–O · 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.