amsterdam to bruges, eurail

No need to make reservations. You can if you want to take the Thalys fast train to Antwerp or Brussels, but you really do not save much time. To use Thalys would not only require a reservation, but additional cost, they may even limit the seats available for passholders.

The intercity trains do not require a reservation and they do not sell out, except maybe for some rare holiday or event. You can go Amsterdam, Rotterdam, Antwerp, Ghent, to Bruges. Usually you can find a train that goes to Antwerp, negating the need to change in Rotterdam.

It seems you already bought the train pass, which is a shame because it’s unlikely it will save you money and it certainly doesn’t save you any hassle. That’s because there isn’t any hassle training from Amsterdam to Bruges to begin with. If you hadn’t already bought the pass all you would have to do is buy an Intercity train ticket from Amsterdam to Bruges. A ticket for the Intercity train is valid on all trains from Amsterdam to Bruges on the day mentioned on your tickets. Intercity trains are mass transit and are just like the subway in New York. Tickets never sell out and you can’t book a specific train nor can you reserve seats. You just get on the train towards Antwerp, leave the train in Antwerp and get on the train to Bruges.
Since you apparently have already bought the pass, you will need to activate it for the day. Once you’ve done that, the process of training to Bruges is the same; train to Antwerp, change to train to Bruges.

https://www.ricksteves.com/travel-tips/transportation/trains

even if you buy the very expensive passholder reservations mandatory on the high(er) speed Thalys train, when you connect to the train to Brugge/Bruges you can't reserve a seat.

thanks everyone...we will be using the pass as we travel, i will have 4 more travel days..thanks again.
steve

thanks everyone...we will be using the pass as we travel

That's how I and others replied.

Your main OP question was about reservations and you said how important that detail is. If you take the International train it is free with your pass and no reservations. If you take the Thalys it is very expensive for the pass-holder (often nearly as much as a discounted regular ticket) to get the mandatory pass-holder reservation, but you don't need to do it ages ahead. The Brussels to Brugge/Bruges train has no reservations and is free with your pass.

The Thalys is a little faster, the International is easier and free with your pass.

thanks..that makes sense.

We just returned from Europe (family of 4) and each had a 5 day Eurail pass. Based on our experience, while we were able to do all the traveling we wanted to do with the passes, we almost had an issue booking our train from Amsterdam to London. We ended up having to change trains in Brussels which was not the end of the world, but the "issue" was that I almost waited too late to make the reservations. As some one else posted, there are only a certain number of seats available on each train for Eurail pass holdovers and not all train times have Eurail pass slots to begin with (if this makes sense). So, end of story is to book as soon as possible to see the most options available.

Note a few additional details, here:

https://community.ricksteves.com/travel-forum/netherlands/amsterdam-to-brussels-to-brugge-back-to-amsterdam-by-train

Perhaps I said it elsewhere, but many local trains (Brussels-Antwerp-Gent-Bruges) are double-decker commuter cars without real luggage racks. Only thin overhead racks like on a bus. Worst case, you stand in the big door vestibule area with your bags, which does not block the door.