Inspect and secure the guard
Check the guard, retaining screw and cutter; fit only an undamaged supplied guard using the matching assembly figures.
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 |
|---|---|---|
| Guard or mounting screw if a replacement is needed | Exact LST300 tool-type part identified by the manufacturer Supplied undamaged assembly, or a replacement confirmed through authorized service | Unverified guard, substitute screw, damaged tabs or housing threadsEnglish p8 Installing the guard; figs D–E |
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.
Is the supplied or installed guard intact and an exact match for figs D–E in your type manual?
- Yes — Check its attachment without touching the sharp cutter.
- No — Cracked, incorrect or damaged guards need the correct part and authorized service.
- Not sure — Keep the battery removed. Save your preparation record and check the matching manual before continuing.
Are the guard tabs, motor-housing ribs, locking slot and original screw intact?
- Yes — An undamaged supplied guard can be fitted as shown.
- No — Do not compensate for damaged tabs or threads with a different screw, tape or force.
- 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 the installed guard
Turn the stopped, battery-removed tool so the spool cap and guard can be seen. Look for splits, missing sections, bent mounting features and a loose screw. Keep clear of the line cutter.
Look for: The guard has no damage and its mounting features can be identified.
Manual: English p8 Installing the guard; figs D–EIdentify whether assembly is needed
If the guard is already correctly secured, leave it in place and continue to the attachment check. For an undamaged supplied guard awaiting initial assembly, remove its supplied screw with a Phillips screwdriver.
Look for: You are either checking the installed guard or fitting the supplied intact part; damaged mounting parts require service.
Manual: English p8 Installing the guard; figs D–EFit the supplied guard if needed
For initial assembly, turn the guard upside down and slide it fully onto the motor housing. Match guard tabs to the housing ribs in fig D and continue until the locking tab snaps into the housing slot. Do not force misaligned parts.
Look for: The tabs engage the ribs and the locking tab occupies its slot.
Manual: English p8 Installing the guard; figs D–ECheck the retaining screw
For initial assembly, insert the supplied guard screw as fig E shows. For an installed guard, check that this screw is present and the guard is firmly retained. No torque value is provided in this task; damaged threads require service.
Look for: The screw arrangement matches fig E and the guard stays firmly in place.
Manual: English p8 Installing the guard; figs D–ECheck the cutter cover and record the result
Only after a new guard is secured, remove the factory covering from the line cutter as the manual directs. Keep fingers away from the cutting edge. Record the mounting result; a missing, damaged or loose guard blocks operation.
Look for: The mounted guard is secure; no factory cover remains when preparing for use.
Manual: English p8 Installing the guard; figs D–E
5. Keep your result
Record what you observed. A completed checklist does not certify that equipment is repaired.
When to check again
Before use and after guard assembly or an impact
Check guard condition before use. The manual does not give a screw torque or a replacement interval.
Manufacturer guidance · English p8 Installing the guard; figs D–ESources & fit
- BLACK+DECKER LST300 instruction manual (manufacturer document, retailer-hosted)English p8 Installing the guard; figs D–E · 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.