Performing the technique
To perform a glide toss, grab a throwable item. Perform a roll and almost immediately (about 6 frames) after throw the item in any direction. The character will then cancel the dodge and throw the item, but seeing as the player's momentum is kept from the roll, the character will slide along the ground.
The traveled distance depends on the character, the type of roll, the direction thrown, and the moment the item was thrown. Generally, the later the item is thrown, the bigger the glide.
Some characters can benefit greatly from the speed boost gained with a glide toss, allowing them to cover large distances in short time. Given the throwing animation's short duration, a glide toss is usually safer than other approach methods.
Uses in competitive play
Due to the fact that items are turned off by default in competitive play, glide tossing is limited in application. However, there are some characters that can produce their own items. For these characters, glide tossing serves as an excellent means of approach. Glide tossing is faster and less punishable than dash tossing an item, and it leaves the character standing at the end, ready to segue into any of their moves. It moves the character forward with the advantages of a forward roll, but without the disadvantages. It also allows the character to throw as fast as their standing item throw, but while moving forward to help advance.
A few characters have truly outstanding glide tosses that allow them to slide much further than others, particularly Pit (highest average distance), Meta Knight (second highest average) and Zero Suit Samus, who can throw her powerful items out of a glide toss during the beginning of a match, immediately attack with d-smash should the opponent be at very low percents, and can then regrab her item once the opponent has been knocked away. Peach also makes an excellent glide tosser, though not quite as powerful; she can combine her floating approach with her long range glide toss at any time to frustrate opponents. She can also glide toss immediately out of plucking a vegetable, which can reduce the lag time between plucking and throwing further, all the while approaching.
While glide tossing is generally limited to characters that can produce items, most characters can glide toss in competitive play if they manage to catch said items. However, some characters gain no distance by glide tossing, and Yoshi (due to his odd shield physics) cannot glide toss at all.
The following characters have the ability to create items that they can use to perform a glide toss:
User BurningCrusader777 from the Smash Boards performed a study on the distance each character can achieve with this technique. There are 4 ways to glide toss, given that throwing up and down is normally the same as a forward throw, except it gives less distance. Forward roll with a forward throw, backward roll with forward throw, forward roll with reverse throw, and backward roll with reverse throw.
Some characters gain no distance in glide tossing, and Yoshi (due to his odd shield physics) cannot glide toss at all.
In Melee, a select few characters can slide forward while throwing in item on the ground, though it is not nearly as noticeable as glide tossing in Brawl. Performing a directional air dodge and then throwing an item can be considered an "aerial glide toss". Captain Falcon and Marth seem to benefit from the grounded glide toss, and Peach and Captain Falcon seem to benefit from the aerial glide toss, though out of those characters, the only one who can generate items is Peach.
Grounded glide tossing
Aerial glide tossing