Recap
The changes in the 34 hour restart have been in the news of late. Last year the FMCSA made two alterations to the 34 hour restart rule. The first change is that there had to be at least 168 hours between the start of two 
34 hour restarts. As long as you have 168 hours between restarts you are fine. The other is that your restart has to contain at least 2 periods between 1am – 5am. Both changes caused chagrin among drivers. Drivers get concerned when they potentially lose productivity.
The changes in the restart rule are something that I can work around. There will be times when I will not use a restart that I am eligible for because I may need it the next week. Remember that you don't have to use a restart every time that you are eligible for it. You may be better off (because of the 168 hour rule) to skip the the restart one week so that you can use it the next week. You can just use a recap.
Then it occurred to me that the vast majority of over the road drivers may not know how to do a recap. It makes sense. Only 18% of over the road drivers have been out here more that 6 years. The original 34 hour restart rule has been around for about 10 years. It makes sense that the many drivers have been using the 34 hour restart and have never used a recap. Add to that the use of ELDs, and it makes me wonder just how many drivers out there have never done a recap. The ELD does the math for the driver. It does not do the thinking for the driver.
Basically we are not allowed to drive after working 80 hours in 7 days. Some will use the 70 hours in 6 days rule, but the majority of OTR drivers use the 7 day rule. Paper log books will usually have a recap chart on the inside cover. Keep track of the hours that you are using every day. If you are using a paper log book use the 
recap section. At the end of my paper log career I used loose leaf paper logs. These were easier for me. If I did make a mistake it was easy to rip up and throw away one sheet and change the mistake than if I were using a book. I kept my logs together in envelopes. I manually did a recap graph right on the envelop.
When I was running heavy hours I kept the graph filled out. That way I could see in advance that I could be running out of hours and ask for a shorter load. It is interesting to not that you could use 8.75 hours forever without running over your 70. When you start compiling 10-12 hour days those hours can run short.
With all things trucking, the intelligent use of math can help you anticipate and avoid problems. Using a recap and keeping track of your hours is an old dog way of doing just that.