Cannot find drain plug on 21 inch bolens lawn mower. I have looked under the mower and there is not the usual square pipe plug.

Here's a video,it's the red bulb Douglas. Bolens Push Mower First Start Of The Year YouTube

Usually the drain plug is located under the deck by the shaft. It looks like a inverse plug. Use a socket wrench to undo it.

If there is no drain plug in the crankcase bottom (under deck), then look for a square-head type plug on the engine side near bottom. If none there, then the mower will have to be tipped on it's side and the oil drained out of the oil fill tube.

If you look under the mower, there will be a square hole that a socket wrench will fit into. It will either be 3/8 or 1/2. You put it in there and start to screw it out. Once loose, it will come right out. It is more than likely plastic.

under mower,remove blade,remove plastic or metal shield,remove blade adaptor that the belt goes around,by now you see the bottom of the engine,look for a square headed plug that a 3/8 inch ratchet with a short extension fits into and remove conterclockwise and have a container to catch the oil )or you may see a plastic plug that a standard wrench would fit or possibly still a ratchet item.( Note : always have your mowers spark plug up,usually in the front and support the front while you are doing the above)
If you dont want to get dirty then buy a vacuum oil extractor and remove the oil through the dipstick hole

no special tool needed.Just use a 3/8 ratchet extension. Fits perfect

What kind of oil did they put in? The drain is on the lowest part of the engine, a small plug either in the block or at the end of a pipe, just find a container to fit under there and pull the plug, then fill it back up with the fresh oil. Don't forget the plug!

look at the side of the engine down low. There should be a pipe plug screwed in that has a square head. Put a drain pan under the area and remove this plug and the oil will drain out. It's best if the engine is warm. You should get 1 1/2 quarts of oil out of it. Let it drain for about 5 minutes and then re-install the pipe plug. Add 1 1/2 quarts of 30W oil and then cut the grass !

may be under the blade plate under the mower, usually a plug with a quarter inch square drive, you can use a ratchet to loosen it if it is quarter drive, maybe a half inch drive

If you look under the mower where the engine shaft comes out of the engine you should see what we call a pipe plug. If will be either a male square which you can use a adjustable wrench on or maybe a 3/8 square female which is what you have on the end of a 3/8 ratchet or 3/8 extension. Hope this is helpful.
donnyb60