Question how can I tenderize my meat without a mallet or
a meat tenderizing tool
Answer The mechanical means that you mentioned are the most effectve. Marinades are flavorings and do little to tenderize meat. Papain a powerful enzyme in pineapple juice will turn the outerlayer of your meat to mush but do little else. Another option is the way you cook it. Braising, the cooking technique that crock pots use, a temp just below boiling combined with moisture will convert tough connective tissue to gellatin but will ruin a lean cut of meat. It will end up like pot roast, gray and stringy but falling apart. The best way to assure beef is at least as tender as it started out is cook it rare or medium rare. That way the coagulation of the protein is at a minimum, the meat will still be juicy and will not be dry and gray like a well done steak.
It you don't have a mallet use a piece of 2x4 turned on edge. Put the meat under a plastic shopping bag on a cutting board to minimize mess and hammer it on both sides till it is about 1/4 inch thick. This can dont to chicken and pork to make cutlets.
Keith