Paul E. Hadlick Jr., a speech clinician in the Montgomery County school system, has been granted U.S. Patent No. 4,203,210 for a shingle striper, a simple tool that looks like a shovel. He's already sold about 700 while the patent was pending.

The tool, which is actually made from a shovel, retails for about $2 and is going like hot cakes, Hadlick says.

This is not Hadlick's first invention. He received a patent in 1960 for a desk for blind children, the braille desk, which he gave to the Montgomery County schools. They now have nine of the desks. And Hadlick says he is working on some other inventions.

Hadlick is a good example of the modern-day small inventor who makes good by producing and selling his own invention to the retail trade.

Patents granted recently to residents of Maryland, Virginia and the District: MARYLAND

David D. Moran of Silver Spring. Surface Effect Ship Internal Sidewall Drag Reduction Device. Patent No. 4,196,686. 3 claims.

Harold A. Gell Jr. of Silver Spring. Orientation System. Patent No. 4,198,635. 42 claims.

David N. Kramer of Stevenson, Stephen E. Long of Baltimore and Alan A. Schneider of Reisterstown. Solvator Plug. Patent No. 4,198,281. 5 claims.

Jerome C. Kremen of Takoma Park. Optical Scrambler for Depolarizing Light. Patent No. 4,198,123. 6 claims.

John C. Munson of Silver Spring. Passive Underwater Target Detection and Locating System. Patent No. 4,198,704. 15 claims.

George R. Olebert of Hyattsville. Trailer with a Dumpling Bottom. Patent No. 4,198,096. 4 claims.

Joseph R. Howell Jr. of Boonsboror.Bong With Full-Bore Removable Plug Standard. Patent No. 4,201,230. 6 claims. VIRGINIA

Gim S. Ng of Newport News. Dual Caliber Revolver. Patent No. 4,197,666. 1 claim.

Tyler K. Olcott of Valentines and Robert M. Miller of Lakeland, Fla. Molded Plastic Article Having a Thermally Shockable Insert Therein. Patent No. 4,198,452. 8 claims.

Ed P. Toms of Arlington. Water Recycling with Solids and Foam Removal. Patent No. 4,197,597. 11 claims.

Clarence Cantor of Alexandria. Proximity Sensor and Method and Apparatus for Continuously Measuring Rail Gauge. Patent No. 4,198,164. 8 claims.

Abul A. M. Ahmed of Arlington. Plasma Energy Production. Patent No. 4,199,402. 2 claims.

James E. Blair of Roanoke and Lois T. Davis of Salem. Process for Decolorizing Pulp and Paper Mill Wastewater. Patent No. 4,199,444. 4 claims.

Ralph W. Carp and John F. Slack of Newport News. Signal Amplification Means. Patent No. 4,198,934. 8 claims.

Gary R. Feldpausch of Richmond. Tent Peg Mallet and Remover. Patent No. 4,198,719. 8 claims.

Virgil L. Frantz of Salem. Dual Filter Assembly for Compressed Gas. Patent No. 4,199,331. 6 claims.

Roy F. Hudsdon and Henry A. Schaefer of Lynchburg. Housing for a Two-Way Radio or the Like. Patent No. 4,199,204. 4 claims.

George R. Welti of Leesburg. 3-Position, 4-Port Waveguide Switch. Patent No. 4,201,963. 8 claims.

George R. Welti of Leesburg. Multibeam Communications Satellite. Patent No. 4,201,992. 5 claims. DISTRICT OF COLUMBIA

William R. Mizelle.Caloric Incapacitating Low-Lethality Projectile. Patent No. 4,204,474. 9 claims.

Alfred B. Levine. Target Panel.Patent No. 4,205,846. 3 claims.

John L. Smith. Electronic Photometer. Patent No. 4,207,533. 11 claims.

Leon E. Wedding. Acoustic Decoy and Jammer. Patent No. 4,207,626. 7 claims.

Claim: Defines the invention and sets the bounds of the monopoly asserted by the inventor.