for me, i have found out hard way. that little metal tool boxes ya pick up like at sears, or a fishing lure box. are not so great. to a point the locks and hinges will bust rather quick or come open on there own.
5 gallon buckets is what i use. when i have the draw bar on the allis chalmers CA. i had some scarp metal laying around. and built a little C shape like support off the rear. then use a couple large bolts like hooks for the handles on the 5 gallon buckets. they work well for when i have the 100 foot cable i use for pulling some smaller size trees out of the woods.
if you have room between front and rear tires and high enough off the ground. drill some holes put a bolt through the frame. and get a large S hook that you can Squeeze one side down and around the bolt. to hang 5 gallon buckets off of.
there be another post in last couple days, of folks using 5 gallon buckets like soundguy and myself to load tools up into in the shop. then carry the 5 gallon buckets around to different projects.
for me it generally requires 2 to 3 buckets for a given project. one for tools, and other 2 for given materials or extra tools.
for chains, 5 gallon buckets tend to be easier. due to you have a lip you can hook end of chain to. and let the rest of the chain get mixed up in the bottom of the bucket without getting into to much of a mess.
if you have a ROPS or FOPS on your tractor. they make good mounting spots for 5 gallon buckets.
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word of warning though. tractors love to bounce. and anything in a 5 gallon bucket, or tool box is likely to bounce out when you least expect it to.