From inside (document excerpt):
Form Number 3352-570 22in Recycler ® Lawnmower Model No. 20041 – 250000001 and up. Parts Catalog Ordering Replacement Parts To order replacement parts, please supply the part number, the quantity, and the description of each part desired. Understanding Reference Numbers Each Identified part in an illustration has a reference number. The reference number for a part also appears in the parts list, along with other information about the part. This catalog uses two special reference number formats, one to indicate parts in a service assembly and another to indicate the quantity of a given part in an illustration.
Service Assembly Reference Numbers Parts in service assemblies have reference numbers in the form a:b. The a represents the reference number of the entire service assembly and the b represents a sequential number unique to each part within the service assembly. Register your product at www.Toro.com For example, a wheel assembly might be identified by reference number 6, the tire by 6:1, the valve by 6:2, and the wheel by 6:3. When you order the assembly identified by reference number 6, you receive all parts identified by reference numbers 6:1, 6:2, and 6:3. However, you may also order any part individually. Reference numbers of this type appear in illustrations and in part lists. Reference Numbers Indicating Quantity In an illustration, if a reference number indicates more than one part, the reference number has the form nX y. The n represents the quantity of the part, the X is the multiplication symbol, and the y represents the reference number. For example, in an illustration, the reference number 2X 37 means that two of the parts identified by reference number 37 are indicated. The Toro Company – 2004 Contents Description Page Housing Assembly 3 Front Axle and Wheel Assembly 4 Rear Axle and Transmission Assembly 5 Transmission Assembly No. 106-3956 6 Engine and Blade Assembly 7 Handle Assembly 8 Electric Start Assembly 9 Rear Bag Assembly 10 Cylinder Assembly Briggs and Stratton 125K050186-E1 11 Crankshaft Assembly Briggs and Stratton 125K05-0186-E1 12 Crankcase Assembly Briggs and Stratton 125K05-0186-E1 13 Carburetor Assembly Briggs and Stratton 125K05-0186-E1 14 Description Air Cleaner Assembly Briggs and Stratton 125K05-0186-E1 Governor Assembly Briggs and Stratton 125K05-0186-E1 Muffler and Fuel Tank Assembly Briggs and Stratton 125K05-0186-E1 Page 15 16 17 Blower Housing Assembly Briggs and stratton 125K05-0186-E1 18 Starter Assembly Briggs and Stratton 125K050186-E1 19 Starter Motor Assembly Briggs and Stratton 125K05-0186-E1 20 Gasket Assembly Briggs and Stratton 125K050186-E1 21 Carburetor Overhaul Kit Assembly Briggs and Stratton 125K05-0186-E1 22 Part Description Abbreviations Part descriptions in this catalog may include the following abbreviations. AR . as required INC . incorporated ASM assembly LH . left hand CARR carriage NI nylon insert DEG degrees PPH phillips pan head FH . flat head PTH phillips truss head GA . gauge PTO power take off HF . hex flange RH . right hand HH . hex head SFH slotted fillister head HHF hex head flange SHH slotted hex head HHFTF hex head flange thread forming SHWH slotted hex washer head HJ . hex jam SPH slotted pan head HLH hex lag head SQH square head HOC height-of-cut SRH slotted round head HS . hex STD standard HSBH . hex socket button head TAP self tapping HSFH . hex socket flat head TTH torx truss head HSH hex socket head WH . wing head HWH . hex washer head HWHTF . hex washer head thread forming HYD hydraulic Footnotes OE Z · Not serviced separately Included in Carburetor Overhaul Kit-Ref. 121. Obtain parts from your local Briggs & Stratton dealer · · Included in Engine Gasket Set-Ref. 358. Included in Carburetor Gasket Set-Ref. 977. 2 3352-570 Housing Assembly