US/Canada border is 8,893 km (includes 2,477 km with Alaska).

That converts to 5526 miles. Subtract Alaska's border (assuming as Guest US stated about Canada that "there is nothing there worth blowing up" (and with apologies to Alaska 'catters. because my years in the Northwest Territories have made me aware just how beautiful the north really is))--that then leaves 3987 miles of border between Canada and the USA to be defended by Canadian troops. Assuming that a space of 50 yards would be an effective distance between troops to prevent the infiltration of people you do not want in the USA, that would require lots of soldiers. How many? Give me a sec. That would require 58.67 soldiers per mile. Multiply that by 3987 and we arrive at the figure 233917. Assuming you'd want 24/7/365 coverage, 701,751 soldiers. Now, let's take a pay rate of $22,000 per soldier per year (excluding the cost of bullets). The cost would be $15,438,522,000. But since that's in Canadian funds, the cost at today's exchange rate would be $12,802,486,999 American. Sounds like a helluva plan, Doug. Good thinkin'.